Ventilation and Explosion Prevention Downloadable Mining Publications

Describes a project conducted by the Bureau of Mines in which the accurate directional drilling of a borehole was demonstrated with the objective of intercepting a designated target. The project was conducted at Navajo Dam in northern New Mexico at the request of the Bureau of Reclamation. (PDF, 2520 KB, 1987)

This paper summarizes the modeling efforts conducted by NIOSH in the U.S. and CSIRO in Australia to address various gas management issues encountered in longwall mines using the application of computational fluid dynamics (CFD) and numerical reservoir modeling for gob inertization and gas control for spontaneous combustion, pre-mining degasification of coalbeds, gob gas venthole design and performance evaluation in longwalls, and gas management during development mining.  (PDF, 462 KB, 2008)

Discusses the evaluation of a seal evaluation method, based on a hydrostatic pressure loading concept, for in-situ testing of seals in an operating mine. (PDF, 6213 KB, 2003-10)

Increasing longwall panel dimensions, particularly face width in gassy coalbeds, may result in unexpected increases in methane emissions. To investigate this problem, continuous longwall face emission monitoring studies were conducted at two adjacent mines operating in the Pocahontas No. 3 Coalbed, where longwall faces were to be extended from 229 to 305 m (750 to 1,000 ft). (PDF, 1919 KB, 1997)

The Bureau of Mines has developed an acoustic test for determining if a rock salt sample is from a "normal" nongassy salt face or from a gassy face where an outburst has the potential to occur. The acoustic test procedure and equipment are described, and raw test results and data analysis are shown. Results are also shown for several salt samples that were analyzed using a laser Raman microprobe. (PDF, 678 KB, 1990)

This study proposes a principle component analysis (PCA) and artificial neural network (ANN) approach to predict the ventilation methane emission rates of U.S. longwall mines and the optimum combination of degasification boreholes based on the given characteristics of the mine. (PDF, 169 KB, 2008)

The Bureau of Mines investigated coal storage silos to determine how gassy coal must be for methane accumulations in a silo to become hazardous and where such accumulations are likely to occur. Methane concentrations were measured in the open space above the stored coal pile, in the pile, and in the reclaiming area. (PDF, 394 KB, 1981)

This Bureau of Mines research study found gas emission rates from an advancing face, and flows and pressure of gas from an exploration drill hole were dependent upon the geology of salt encountered in a domal salt mine. This information suggests a greater methane emission hazard from the anomalous zone than from the associated normal salt. (PDF, 33349 KB, 1984)

Gas occurs in coalbeds in an adsorbed and a free gas state. Adsorbed gas is stored in the micropore structure and its transport is governed by Fick's law. The free gas occurs in the fracture system and flows according to Darcy's law. These two modes of mass transport are interdependent. Production decline curves of coal-gas wells are of the constant percentage decline type and, thus, show no indications of flow characteristics peculiar to coal-gas reservoirs. The effectiveness of surface boreholes as a degasification scheme depends upon both good fracture permeability and a high fracture density. Conventional methods of reservoir engineering analysis are not applicable to coalbeds. (PDF, 1022 KB, 1969)

Air quantity-pressure and methane concentration surveys were conducted in accessible portions of an area being pillared in a Pittsburgh coalbed mine in West Virginia. These included two mined-out and three active butt headings and a bleeder system. The particular mine workings were started in virgin coal directly from a set of main headings; the main reason for the study was the difficulty usually encountered in adequately bleeding the gobs under such conditions. (PDF, 597 KB, 1973)

The U.S. Bureau of Mines conducted a worldwide literature review of bleederless ventilation practices to evaluate their use as a spontaneous combustion control measure in U.S. coal mines. This report describes the types of ventilation systems used throughout the world and the spontaneous combustion risks associated with these systems. (PDF, 3168 KB, 1994)

This paper describes the results of a NIOSH borehole monitoring experiment (BME) on an active longwall panel. (PDF, 459 KB, 2008-06)
                                          

Researchers with NIOSH studied the electrical equipment ignition sources for the Brookwood and other disasters to develop recommendations for preventing similar disasters.  (PDF, 373 KB, 2007)

Investigation of the geologic and mining factors influencing the migration of longwall gob gas with a goal to optimize methane drainage strategies to reduce the volume of gob gas that reaches the underground workplace. (PDF, 175 KB, 1999)

The Bureau of Mines investigated the physical characteristics of and roof instability problems associated with clay veins. This was accomplished by observing and mapping clay veins in surface and underground mines. The occurrence and origins of clay veins were also investigated to determine predictive capabilities. (PDF, 3464 KB, 1987)

The natural vertical fracture system in bituminous coalbeds is called cleat. Cleat orientation commonly controls the direction of mining with major development paralleling the face cleat. Previous researchers have categorized the origin of cleat as endogenetic, relating the origin of cleat to compaction and coalification, and exogenetic, relating the origin of cleat to tectonic forces. In the coalbeds studied for this report it was found that tectonic forces were the controlling factor of cleat formation. Cleat orientation in other bituminous coalbeds in Virginia, Utah, Oklahoma, and central Pennsylvania showed a relationship to local structure. Directional permeability of coal is directly related to cleat. Holes drilled perpendicular to the face cleat yield from 2.5 to 10 times the amount of gas released as compared with holes drilled perpendicular to the butt cleat. (PDF, 1031 KB, 1974)

This study presents a numerical investigation of geological discontinues in the coalbed using reservoir simulations of the effects of partings and permeability facies and lithotype changes on the production performances of vertical and horizontal degasification boreholes, as well as the emissions during longwall operations.  (PDF, 571 KB, 2008)

This article describes the Coal Dust Explosibility Meter (CDEM), a hand-held instrument developed by NIOSH, which uses optical reflectance to measure the explosibility of a rock dust and coal dust mixture, which is now commercially available. (PDF, 198 KB, 2008-06)

The accumulation of coal dust in underground coal mines can be rendered nonexplosible by adding efficient quantities of inert rock dust, such as limestone dust. NIOSH has devised a prototype handheld instrument that can provide a direct assessment of the potential explosibility of a coal and rock dust mixture. (PDF, 1759 KB, 1997-10)

NIOSH and MSHA conducted a joint survey to determine the range of coal particle sizes found in dust samples collected from intake airways of U.S. coal mines. (PDF, 56 KB, 2006-08)

NIOSH and the Mine Safety and Health Administration (MSHA) conducted a joint survey to determine the range of coal particle sizes found in dust samples collected from intake airways of US coal mines. The results indicate that particle sizes of mine coal dust in intake airways are finer than those measured in the 1920s. This finer size coal dust in intake airways would require more incombustible matter to be effectively inerted than the 65% incombustible specified in current regulations.  (PDF, 742 KB, 2007-07)

Information was collected on the geologic conditions, mining techniques, and engineering parameters at five bump-prone mines. Two geologic conditions have been found to cause the occurrence of bumps in the eastern United States: (1) relatively thick overburden and (2) extremely rigid strata occurring immediately above and below the mine coalbed. Additionally, the probability of bump occurrence is increased by certain mining practices that concentrate stresses during retreat mining in areas where geologic conditions are conducive to bumps. Mining plans that permit the development of pillar line points or long roof spans that project over gob areas should be avoided because these features may contribute to the occurrence of bumps. (PDF, 3464 KB, 1987)

The focus of this paper is the use of a GAG 3A jet engine system to either combat large out-of-control fires or render an entire mine inert when access to problem areas is difficult or impossible. (PDF, 941 KB, 2005-06)

This report describes a multipurpose borehole used for both degasification and the production of commercial-quality gas. The multipurpose borehole was drilled into a barrier pillar, and seven horizontal degasification holes and one pressure point hole were drilled radially out from its perimeter. This study indicates that horizontal boreholes drilled into a coalbed from the bottom of any shaft will effectively remove gas from the Pittsburgh coalbed. (PDF, 1005 KB, 1975)

An evaluation of strategies for monitoring methane levels during roof bolting in an extended cut entry. (PDF, 145 KB, 1999-04)
                                                

This paper contrasts the full-scale explosion and hydrostatic testing of mine seals using a simple dynamic system model and principles. (PDF, 785 KB, 2008-09)

This Bureau of Mines report describes and compares the procedures, capital investments, and operating costs of rotary and in-hole motor drilling techniques used to drain methane gas from the Pittsburgh coalbed in an underground mine located in southwestern Pennsylvania. (PDF, 2404 KB, 1985)

The Bureau of Mines conducted studies to compare the effectiveness of the cross-measure borehole system with that of surface gob holes on two successively mined retreating longwalls in the Lower Kittanning coalbed. Only the cross-measure system was in operation on panel A; on panel B, both systems were in operation. In addition, the cross-measure boreholes on panel B were drilled parallel to the face, whereas those on panel A were drilled at a 45 degrees angle with respect to the longwall axis. (PDF, 1157 KB, 1986)

Samples of gas were obtained directly from the coalbed during drilling of horizontal and vertical boreholes in six different formations. The samples were analyzed by gas chromatography. (PDF, 352 KB, 1973)

This paper focuses on the flow patterns within the gob under three different ventilation systems: one-entry and two-entry bleederless systems, as well as a three-entry bleeder system. (PDF, 599 KB, 2006)

Deeper surface mining and deeper highwall penetration depths have lead to more frequent encounters with methane gas. While this coal is remotely mined from the surface, underground ignitions of methane have propagated to the surface and injured miners. Methods described in this paper show how this hazard can be correctly monitored and controlled for auger type highwall mining machines. (PDF, 953 KB, 1997)

The cross-measure borehole technique is being studied as an alternative to the use of surface gob boreholes as a means of controlling methane in gobs during longwall mining. Small-diameter holes are drilled from underground locations into strata overlying the mined coalbed. When the roof strata are fractured by the mining operation, a partial vacuum applied to the boreholes draws the methane out of the fractured strata and prevents it from entering the mine ventilation system. Tests in the Upper Kittanning coalbed showed that 50 pct of the methane produced by the longwall mining operation was captured by the cross-measure boreholes. Borehole inclination and penetration into the gob are two important borehole parameters that affect the performance of the cross-measure borehole system. (PDF, 2398 KB, 1983)

The Bureau of Mines conducted research to determine the effectiveness of long holes drilled in solid virgin coal in degasifying an area of the Pittsburgh coalbed showing that horizontal holes drilled into a virgin coalbed from the bottom of any shaft will effectively remove methane gas in commercial quantities from the Pittsburgh coalbed. The gas drained to date is six times the gas estimated to be in the area subtended by the holes. Methane emissions at the working face of 1 west mains, Federal No. 2 Mine has been reduced by 50 pct, proving the value of methane drainage by horizontal degasification holes drilled from shaft bottoms ahead of mining. (PDF, 1298 KB, 1976)

A 5-hole pattern was drilled from the surface at a site near Oak Grove, Jefferson County, Alabama, to degasify the gassy Mary Lee coalbed in advance of mining. Gas and water production was monitored for 1 year, 4 months to allow gas flow to stabilize fully. A thickened water stimulation treatment was designed and applied in one hole of the pattern to evaluate this degasification technique for the Mary Lee coalbed. Results indicated that the use of vertical boreholes coupled with hydraulic fracturing in advance of mining the Mary Lee coalbed would provide for more rapid degasification and could provide a possible source of natural gas. (PDF, 767 KB, 1974)

The Bureau of Mines has developed several techniques for draining methane from coalbeds in advance of mining. Drilling long horizontal holes from an underground location is one such technique, which was successfully demonstrated in the Pittsburgh and Sunnyside coalbeds. The same technique has now been applied in the Mary Lee coalbed at Jim Walter Resources, Inc. (PDF, 820 KB, 1982)

The Bureau of Mines is in the process of degasifying a virgin area in northern West Virginia from the base of an 839-foot-deep vertical borehole. After 180 days of degasification, 91 million cubic feet of gas had been removed from the affected virgin area. This represents 60 to 70 percent of the gas calculated to be contained in the area of coal affected by the holes. (PDF, 2033 KB, 1973)

The Bureau of Mines conducted research to degasify a virgin block of coal in the Beckley coalbed using long horizontal holes drilled in an array from the bottom of a ventilation air shaft. Eight horizontal holes and an in situ pressure hole were drilled in a radial pattern. The investigation showed the shaft was in a basin saturated with water, which resulted in low gas flows from holes. Methane face emissions, which were measured as a section advanced toward the shaft, were reduced about 77 pct. All holes were grouted before the area around the shaft was mined. (PDF, 1139 KB, 1982)

This study describes the development of an expert classification system used as a decision tool which can be usedfor degasification system selection using site -and mine-specific conditions. (PDF, 678 KB, 2009)

An oil well penetrating the Pittsburgh bituminous coalbed in northern West Virginia was plugged and safely mined through 3 months later. Effectiveness of the plugging in preventing reservoir gas from entering the mine through the well hole was verified by continuous monitoring of the mine air for indications of sulfur hexafluoride. Three other wells were also plugged using various techniques. (PDF, 1473 KB, 1972)

NIOSH, in collaboration with the Mine Safety and Health Administration, the mining industry, and seal manufacturers, conducted a series of full- scale experiments to evaluate the explosion-resistant characteristics of several new seal designs for rapid deployment during mine emergencies. These seals can be deployed in less than 12 hours and can withstand explosion overpressures in excess of 140 kPa (20 psi). These novel seal designs use available mine materials, do no require conventional rib hitching and, more importantly, can substantially reduce exposure time for coal miners during sealing and mine recovery operations. (PDF, 955 KB, 2004)

Reports on NIOSH full-scale experiments to evaluate the explosion-resistant characteristics of several new seal designs for rapid deployment during mine emergencies. (PDF, 2280 KB, 2003)

Examination of several coalbeds in Walker County, Alabama, Cambria, Greene, and Fayette Counties, Pennsylvania, and Caleigh and Wyoming Counties, West Virginia, indicates that cleat orientations are similar throughout a vertical sequence of strata. Studies of cleat orientation were carried out in underground mines that are operating in separate coalbeds vertically above one another. The largest variation of cleat directions between adjacent coalbeds occurs where a large horizontal distance separates two sample locations. Cleat orientations for deeper coalbeds are most reliable where the data are taken from directly above. (PDF, 867 KB, 1976)

Four coreholes were drilled (two before and two after mining) at a longwall mine in the Lower Kitanning coalbed to obtain coal and rock samples from overlying strata to determine their gas content at various times in the mining cycle. Test results indicate that 91 pct of the gas removed from the overlying strata came from coalbeds. Further analysis indicated that only 40 pct of the total gas produced from the panel actually came from the strata directly overlying the panel. The remaining volume of gas production probably migrated to the longwall gob from overlying, and perhaps underlying, strata immediately adjacent to the panel and perhaps from greater distances downdip because of the establishment of a long-term pressure gradient. (PDF, 1166 KB, 1992)

This study presents an approach using coalbed methane reservoir modeling and an artificial neural network (ANN) design for prediction and optimization of methane inflows and ventilation air requirements to maintain methane concentrations below statutory limits. (PDF, 1131 KB, 2007-11)

This paper describes the development of reservoir models for the longwall mining environment and their application for investigating the influence of various completion design parameters on the methane drainage effectiveness of gob gas ventholes. (PDF, 264 KB, 2006)

This article focuses on U.S. Bureau of Mines (USBM) and NIOSH research to examine factors that had a significant influence on mine face ventilation design during the past century. (PDF, 2404 KB, 2007-08)

A new protocol based on rigid arch loading of the structure is proposed to determine the true transverse load capacity of block stoppings. The rigid arch tests have shown that the load capability is dependent on the physical properties of the block and geometric properties of the wall, not the sealant. (PDF, 338 KB, 2006-06)

This paper describes the application of a finite difference program to develop a geomechanical model that predicts permeability changes within the rock mass. (PDF, 393 KB, 2005)

Describes a simple, inexpensive test to measure the methane content of coal samples obtained from exploration cores. The results of tests are summarized in tabular form. These results include data on the gas content of 125 coalbeds in 15 states. (PDF, 1830 KB, 1981)

The applicability of the "direct method" for determining the methane content of virgin coalbeds was tested. Preliminary results indicate that the direct method, when applied to exploration cores, can be successfully used to estimate coalbed gas content and also approximately predict the total gas emission from a prospective mine located in the coalbed at the exploration site. (PDF, 612 KB, 1973)

The Bureau of Mines is cooperating with the U.S. Department of Energy in a directional degasification project at the Emerald Mine near Waynesburg, Pennsylvania. This project is designed to combine the highly successful underground horizontal degasification technology with surface drilling methods. The objective of this program is to demonstrate that directional drilling can be used as a technique for degasifying coalbeds ahead of mining to reduce the hazards of methane-air explosions in coal mines.  (PDF, 734 KB, 1979)

A 3-inch pilot hole was directionally drilled to intercept the freeport coalbed horizon horizontally at Mather, Pennsylvania, as part of a Bureau of Mines degasification project. The original concept was to continue the horizontal drilling into the coalbed, after the initial intercept, with a total of three horizontal holes eventually being completed.  (PDF, 1013 KB, 1977)

The Bureau of Mines conducted an experimental degasification project in Island Creek Coal Company Virginia Pocahontas No. 5 Mine. Methane from the overlying Pocahontas No. 4 Coalbed was entering mine workings in the Pocahontas No. 3 Coalbed through fractures in the roof rock. Small-diameter (1-5/8-inch) holes were drilled into the overlying coalbed to reduce the gas pressure and intercept methane flows, which were piped to the surface through an underground 6-inch- diam steel pipeline. Methane flows into the mine were reduced by 47 pct. (PDF, 968 KB, 1979)

Three long horizontal holes were drilled from a directionally drilled surface hole at the Emerald Mine near Waynesburg, Pennsylvania. The purpose was to adapt the technique of directional drilling for use in draining methane from coalbeds. (PDF, 6348 KB, 1982)

The use of a partially slotted 6.5-Inch-inside-diameter vertical pipe to remove methane from a longwall gob area at a depth of 2,260 feet in the Pocahontas No. 3 Coalbed was investigated. The value of gas removed by such a pipe under free-flow conditions was found to equal the cost of the installation in this case. Approximately 25 percent of the available methane passed through the pipe without the use of an exhauster; an additional 10 percent was removed when an exhauster was employed. The diversion of methane through a vertical slotted pipe to the surface permitted the use of increased mining rates and decreased the ventilation air requirements. (PDF, 2499 KB, 1972)

This paper describes ignition tests on pulverised coal suspensions using a suite of coals of different rank and from different countries of origin and over a range of oxygen and coal concentrations of interest for oxyfuel combustion. (PDF, 112 KB, 2007)

Tests were conducted in a full-scale ventilation gallery with a model mining machine that simulated airflow created by a dust scrubber. The results showed that operation of machine-mounted scrubbers improved face ventilation when blowing ventilation is used by increasing both the intake flow and the quantity of air reaching the face. (PDF, 441 KB, 2006-06)

Tests were conducted in a full-scale ventilation gallery to determine the influence of mining machine-mounted water sprays on airflows and methane concentrations at the face when blowing ventilation systems are used. Test results using different spray arrangements and water pressures showed that operation of the machine-mounted sprayers can improve face ventilation effectiveness by increasing the velocity of airflow moving toward and away from the face. The improved ventilation resulted in reduced methane levels near the face. (PDF, 380 KB, 2006-06)

This research evaluated the quality of dust dispersion in the Siwek 20-L chamber using Pittsburgh coal, Gilsonite, and purple K dusts. (PDF, 2264 KB, 2006)

In studies conducted by the Bureau of Mines, two test areas were hydraulically stimulated and exposed by mining: one in the Pittsburgh coalbed at the Vesta No. 5 Mine, Washington County, Pennsylvania; and one in the Illinois No. 6 Coalbed at the Inland Mine, Jefferson County, Illinois. Induced fractures were contained totally within the coalbed with no adverse effect on the stability of associated rock strata. Induced fractures were vertical and were propagated normal to the direction of least residual tectonic stress. Gas production was increased fivefold to twentyfold by hydraulic stimulation. (PDF, 2704 KB, 1977)

Stimulated vertical boreholes are an effective means of removing gas from coalbeds in advance of mining. This Bureau of Mines report examines the coal mine roof damage potential of stimulation treatments. Twenty-two government-sponsored stimulation treatments have been mined through to determine the effects on the coalbed and roof strata. (PDF, 3458 KB, 1987)

Research to determine how machine-mounted water sprays and a scrubber interact to reduce methane levels and what spray configurations provide the best face ventilation when used with a scrubber. (PDF, 320 KB, 2001)

Past studies with blowing face ventilation systems have shown that using a machine-mounted scrubber and water sprays can reduced methane levels at the face. The current research was conducted to determine how the sprays and scrubber interact to reduce methane levels, and what spray configurations provide the best face ventilation when used with a scrubber. (PDF, 311 KB, 2001)

The Bureau of Mines estimated the methane content of a coal, which depends primarily upon rank and pressure, from the adsorption equation V = kPn, where k and n are constants related to rank. By incorporating corrections for moisture, ash, and temperature, and estimating pressure and temperature as a function of depth, the methane content of coal in place can be estimated . Although estimated values were consistently high for several high-volatile bituminous coals from an area where the pressure is known to be less than hydrostatic, the estimated methane content for most coals shows reasonable agreement with values determined by the direct method. (PDF, 820 KB, 1977)

Provides guidelines for more effective use of the ultrasonic anemometer. (PDF, 215 KB, 2004-05)
                                                                               

Examines a procedure for measuring the response time of machine-mounted methane monitors (PDF, 351 KB, 2002)
                                                               

The Bureau of Mines used sulfur hexafluoride (sf6) tracer gas to evaluate the effectiveness of gob ventilation and/or sealing practices at three coal mines, each having different problems associated with their mined-out areas. The purpose of these ventilation studies was to better understand whether current techniques employed for ventilation or sealing are successful at minimizing the potential for gob fires and explosions. (PDF, 1208 KB, 1986)

Production trends were analyzed for 82 gob gas ventholes on 7 longwall panels in the Lower Kittanning Coalbed, Pennsylvania. (PDF, 1029 KB, 1994)
                           

Evaluation of the strength characteristics and air leakage resistance of numerous innovative seal designs and ventilation control structures for use in underground coal mines. (PDF, 6078 KB, 2002)

Report on a series of performance tests conducted on the IYONI II methanometer. Testing methods included use of a calibration fixture, an environmental test box and a full scale test gallery. (PDF, 411 KB, 2003)

The National Institute for Occupational Safety and Health used ground penetrating radar technology to determine if each of three test mine seals were uniformly constructed. The results suggest that GPR could be used as a tool to evaluate mine seal characteristics and construction uniformity. (PDF, 1695 KB, 2005)

This paper describes test procedures used to evaluate performance of methane monitors that could be used underground for continuous personal monitoring of methane. The information in this report provides data that allow the reader to make side-by side comparisons of these instruments. (PDF, 415 KB, 2005)

Strength characteristics and air leakage resistance of seals and designs of water traps used in underground coal mines were evaluated in a joint effort by the Pittsburgh Research Center and the Mine Safety and Health Administration. The efficacies of various seals in limiting air leakage from a sealed area following an explosion were tested. (PDF, 1584 KB, 1996)

NIOSH cooperated with Tecrete Industries Pty. Ltd. and BHP Australia Coal to evaluate the strength characteristics and air leakage of four seal and two stopping designs for use in underground coal mines. (PDF, 4206 KB, 1999)

The U.S. Bureau of Mines conducted explosion tests on various full- scale cementitious bulkheads used in abandoned mine areas to evaluate the ability of the bulkheads to withstand gas explosion overpressures of 20 psig. Tests were performed on 120-ft2 solid- concrete-block seals of varying thicknesses and designs. Of the seven solid-concrete-block seals tested, only the standard-type seal, having a 16-in thickness, keyed at the floor and ribs, all joints mortared, wedged at the roof, and a center pilaster, maintained its integrity when subjected to a 20-psig pressure wave. (PDF, 1274 KB, 1991)

A project to evaluate the South African bagged stone dust explosion barrier was successfully completed at the NIOSH Lake Lynn Experimental Mine. (PDF, 658 KB, 2001)

This study presents a reservoir modeling approach to investigate the relative effects of different coalbed parameters on the migration of methane into development entries. This work shows that coupling reservoir simulations with linear modeling yields a technique that can be applicable to different coalbeds. (PDF, 663 KB, 2008-09)

The Bureau of Mines investigated factors that influence the formation of methane and other hydrocarbon gases in coal, which is an integral part of the coalification process. (PDF, 737 KB, 1978)

This joint MSHA and NIOSH study was designed to simulate actual explosion accidents in coal mines where some crosscut stoppings near the ignition location survived the initial explosion pressure pulse, but stoppings farther away were destroyed. The construction and testing methods, explosion test data, and postexplosion condition of each stopping design are presented in this report. (PDF, 23831 KB, 2008-11)

NIOSH and the Mine Safety and Health Administration (MSHA) conducted joint research to evaluate explosion blast effects on mine ventilation stoppings at the NIOSH Lake Lynn Experimental Mine. The LLEM data showed that a total pressure of 52 kPa (7.6 psi) destroyed the solid-concrete-block stopping, ~36 kPa (~5.2 psi) destroyed the hollow-core concrete-block stopping, and 9 kPa (1.3 psi) destroyed the steel panel stopping. (PDF, 233 KB, 2006-06)

This report presents a historical framework detailing the impact of geologic features on excess gas emissions and resultant mine explosions. It also provides operators with specific information on recognizing and alleviating potential hazards from methane emissions related to these geologic features. (PDF, 799 KB, 2008-04)

Although methane explosions are dangerous, those that involve coal dust are even more so. If exploding methane disperses and ignites the coal dust that has accumulated on the mine ribs and floor, the burning coal dust immeasurably increases the strength of the explosion. Such methane-dust explosions are prevented by inerting the coal dust in a way that prevents the exploding methane from igniting it. This chapter discusses the dust hazard and how it is prevented in U.S. coal mines. (PDF, 4851 KB, 2006)

Seals are used in underground coal mines throughout the United States to isolate abandoned mining areas from the active workings. Prior to the Sago Mine disaster in 2006, mining regulations required seals to withstand a 140-kPa (20-psig) explosion pressure (30 CFR4 75.335(a)(2)). However, Program Information Bulletin No. P06-16 issued by MSHA on July 19, 2006, requires seals to withstand a 345-kPa (50-psig) explosion pressure. The recently enacted MINER Act requires MSHA to increase this design standard by the end of 2007. This report provides a sound scientific and engineering justification to recommend a three-tiered explosion pressure design criterion for new seals in coal mines in response to the MINER Act. The recommendations contained herein apply to new seal design and construction in U.S. coal mines. (PDF, 2768 KB, 2007-07)

This paper outlines the legal standards and methods for protecting underground coal mines in the United States from explosions of methane gas and coal dust. New research will also be presented on the inertization of float coal dust in mines through the addition of inert stone dust and on the application of the Coal Dust Explosibility Meter, a handheld device developed by NIOSH to directly measure the explosibility of a coal dust - limestone dust mixture based on optical reflectivity. (PDF, 46 KB, 2007)

The Pittsburgh Research Laboratory of NIOSH conducted a study of the explosibility of various metals and other elemental dusts, with a focus on the experimental explosion temperatures. The data are useful for understanding the basics of dust cloud combustion, as well as for evaluating explosion hazards in the minerals and metals processing industries. (PDF, 1281 KB, 2007-07)

NIOSH conducted a study of the explosibility of various metals and other elemental dusts dispersed in air, with a focus on the experimental explosion temperatures. The data are useful for understanding the basics of dust cloud combustion, as well as for evaluating the explosion hazards in the minerals and metals processing industries. (PDF, 1476 KB, 2006)

The face ventilation measurement method developed by the Bureau of Mines involves releasing a small volume of tracer gas (SF6) on the off-curtain side of the working face at the start of the mining cycle. At the same time, gas bottle samples are taken in the immediate return airway. The gas samples are analyzed, and a curve is drawn of SF6 concentration versus time. From this curve, the percentage of gas removed per time is calculated. The method was shown to be a simple and effective way of evaluating face ventilation systems. (PDF, 457 KB, 1980)

During the 20th century, the increased emphasis on worker health and safety and the advent of new mining equipment and methods led to many changes in mine face ventilation practices. This paper examines factors that had a significant influence on mine face ventilation design during the past century. (PDF, 843 KB, 2007-02)

Develops criteria for selecting the best machine locations for monitoring methane and gives recommendations for revising methane action levels for alternative sampling locations. (PDF, 268 KB, 2001-06)

The Bureau of Mines has designed and put into operation a fail-safe control system for use in underground coal mines equipped with methane drainage pipelines. This control system can detect certain unsafe conditions and respond by automatically shutting off the flow of methane from the degasification borehole to the drainage pipeline. MSHA has inspected and tested this system and permitted its use in two mines. (PDF, 1027 KB, 1980)

The flow characteristics of both vane-axial and propeller fans were investigated and tested at four large-opening mines to assess the effects of fan location on recirculation and entrainment. Either fan type can be used for most auxiliary applications. However, this research has shown that the optimum placement and use criteria for propeller fans differ from those promulgated by the U.S. Bureau of Mines for vane-axial fans. (PDF, 310 KB, 2006-06)

Two types of flammability limits have been measured for various dusts in the Fike 1-m3 (1000-L) chamber and in the Pittsburgh Research Laboratory (PRL) 20-L chamber. (PDF, 898 KB, 2000-05)

An experimental program was conducted to evaluate the accuracy of some current methods for predicting the flammability of gas mixtures containing hydrogen and flammable or nonflammable volatile organic compounds (VOCs) in air. (PDF, 314 KB, 2000-05)

This paper reports the results of flammability studies for methane, propane, hydrogen, and deuterium gases in air conducted by the Pittsburgh Research Laboratory. (PDF, 537 KB, 2000-05)

Seven degasification wells have been completed in the Pittsburgh coalbed at the New Emerald Mine near Waynesburg, Pennsylvania. The Bureau of Mines performed stimulation treatments on five of the wells to show that this is a feasible and economical means of degasifying part of a coalbed. On the day following stimulation, gas production ranged from a few hundred cubic feet per day to more than 100,000 cu ft/day. (PDF, 478 KB, 1978)

This chapter provides guidelines for determining the gas content of coalbeds, estimating the gas-in-place, and predicting gas flow and emissions before and during coal mining operations. The techniques are discussed briefly in the following sections. However, detailed information on the techniques is provided in the cited references. (PDF, 4851 KB, 2006)

Because of the high number of accidental methane gas ignitions in metal and nonmetal mines, the Bureau of Mines searched for a simple guideline that would allow mine personnel to evaluate the methane hazard in a given mine. Air samples were collected by the Bureau in 53 metal and nonmetal mines and analyzed for trace evidence of methane gas. There was no consistent correlation between commodity mined and methane concentration, nor was there a correlation between mine depth and methane concentration. Neither of these factors can be considered a guideline for predicting methane hazards. (PDF, 442 KB, 1979)

This paper presents a statistical analysis of frictional ignitions in the U.S. from 1983 to 2005. Various factors were considered, including mining machine type, state, basin, coalbed, coalbed production, mining method, production, productivity, mine type, and total emissions. (PDF, 230 KB, 2007)

NIOSH researchers studied US underground coal mine explosions over a 30 year period to identify the ignition sources and ignition locations responsible for the most severe explosion events resulting in death. Recommendations are provided for electrical equipment design and installation to prevent future disasters. (PDF, 92 KB, 2009-01)

The Bureau of Mines has developed a practical methodology for determining occluded gas contents of domal rock salt samples. The method, which is portable and fieldworthy, provides results in 5 min or less. Results can be used to identify gas-enriched zones, and thus may aid mine operators in production planning or ventilation design. The test method is based on the relationship between gas content and the acoustic response of salt samples as they are dissolved in water. (PDF, 1250 KB, 1987)

The Bureau of Mines conducted drilling studies in the Pocahontas No. 3, the Pittsburgh, and a western coalbed to establish the gas migration characteristics for each. Caving in drill holes prevented pressure measurements in the western coalbed. The Pittsburgh coalbed contained intersecting clay veins which formed gas pressure cells. Although these geological features hamper mining, they can be used to control the flow of methane into a mine working. Methane control techniques are proposed for the Pittsburgh and Pocahontas No. 3 coalbeds.  (PDF, 1000 KB, 1969)

In this paper, single-component gas sorption and transient diffusion processes are described within coal matrix exhibiting bimodal pore structure. (PDF, 803 KB, 2009-01)

Methane and other hydrocarbon gases, byproducts of coalification, are emitted from coal at widely varying rates and often present ventilation problems during mining. The air in some coal mines apparently contains no methane. To determine if coals from mines which had no history of detectable gas emission contained adsorbed methane, samples of coal at the shaft bottom and at an active face were obtained and placed in sealed metal cylinders. The atmosphere around the coal was sampled and analyzed by gas chromatography. Methane, ethane, ethylene, propane, propylene, and butane were found to have been desorbed from these coals. Hydrogen and helium were also detected. An estimate of the amount of residual gas per ton of coal indicated that coal samples from the active face generally contained more adsorbed gas than coal samples obtained from the shaft bottom. (PDF, 504 KB, 1973)

Vacutainers are employed by the Bureau of Mines and the Mining Enforcement and Safety Administration for sampling mine air and other atmospheres containing fixed gases, low-molecular-weight hydrocarbons, and products of combustion. Tests were conducted to study shelf life of evacuated samplers prior to sampling and also to check the stability of sampled gases prior to analysis. An unexplained phenomenon, slow accumulation of carbon monoxide in evacuated samplers, occurred after a few weeks of storage; levels were low but increased with time and could pose a problem for critical applications. Storage at low temperature was found to be effective in halting CO release. (PDF, 343 KB, 1978)

A geologic study of Mines 32 and 33 in Cambria County, Pennsylvania, was conducted as part of a methane control research program. The study shows that methane emission in these mines is more closely related to roof falls and emission from strata above the Lower Kittanning coalbed than to any other single factor. (PDF, 1919 KB, 1973)

A Bureau of Mines geologic study of Pennsylvanian and Permian coalbeds in southwestern Pennsylania was undertaken to determine the effects of coalbed geology and petrology on in situ coalbed gas contents. A total of 88 samples from 24 coalbeds were collected for direct-method testing to determine gas content. The samples were also analyzed for petrographic composition, chemical composition, and vitrinite reflectance values. Corehole information was used to generate isopach maps and geologic cross sections useful in data interpretation. (PDF, 1423 KB, 1988)

A series of geological surveys were completed in six coal mines. The aim of these surveys was to study the overall geology of the coalbed, and to use the resulting data to evaluate the influence of the geological characteristcs of the coalbed on safe and efficient coal extraction. This report explains the advantages of geologic maps and fence diagrams in coal mining and how the knowledge gained from such geologic investigations of mines can help control many underground problems. (PDF, 1159 KB, 1975)

This Bureau of Mines study reviews the geological factors that affect methane in the Beckley coalbed in southern West Virginia, including overburden, coalbed structure, type and changes in lithology above and below the Beckley coalbed, and presence of fractures in the coal and rock adjacent to the Beckley.  (PDF, 2292 KB, 1976)

Two degasification test boreholes were drilled to depths of 1,238 and 1,212 feet on Bureau of Mines property at Bruceton, Pennsylvania, as part of the Bureau of Mines long-range coal degasification program. The holes provided detailed geologic information and geologic sections, which were correlated with regional stratigraphic cross sections prepared by the Pennsylvania geological survey.  (PDF, 1023 KB, 1977)

The Upper Freeport coalbed was studied in Fayette County, Pennsylvania. This coalbed lies about 650 feet below the Pittsburgh coalbed and contains the largest remaining reserves of any coalbed in the county. Coal and overburden isopachs, structure and joint pattern maps, and a fence diagram were prepared using data from gas and oil exploration logs and coal outcrops. These maps will aid in determining the need and/or feasibility of degasifying the Upper Freeport coalbed in the study area. Much of the coalbed in this area is under 600 to 1,400 feet of overburden, where the gas content is estimated to be between 140 and 300 cu ft/ton of coal, for a total of 190 to 400 billion cubic feet of methane in this coalbed in Fayette County. (PDF, 1337 KB, 1977)

The Bureau of Mines established geologic factors affecting the mining of the Lower Kittanning coalbed to aid in coalbed minability studies and examined the occurrence of "wants" (places where coal is missing) and types of unstable roof rock strata. Trends established from mapping, including prediction of areas of high methane emissions, were extrapolated to unmined areas.  (PDF, 1759 KB, 1979)

A geologic study of the Mary Lee Group of coalbeds in the Black Earrior Coal Basin was undertaken to examine coal stratigraphy and determine regional trends and extent of the coalbeds. The area investigated encompasses 835 square miles in Jefferson, Walker, and Tuscaloosa Counties, Alabama. More than 700 core logs were used to construct a structure map, coal, interval, and overburden isopachs, and cross sections. (PDF, 2192 KB, 1976)

This study covers 25 underground mines that were active in the Upper and Lower Freeport and Lower Kittanning coalbeds in 1976. The coal ranges from low to medium volatile in rank. Seven mines emit more than 100,000 cfd of methane gas; those mines are the deepest and largest producers. The methane gas content of three core samples of the Lower Kittanning coalbed was estimated by the direct method. Results suggest that methane control problems will be encountered in the future as deeper coal is mined. (PDF, 3334 KB, 1979)

In this report, several practical guidelines are recommended for controlling longwall coalbed methane. All predictions are based on determinations made for the Pittsburgh Coalbed in southwestern Pennsylvania. (PDF, 3861 KB, 2008-03)

This handbook describes effective methods for the control of methane gas in mines and tunnels. It assumes the reader is familiar with mining. The first chapter covers facts about methane important to mine safety, such as the explosibility of gas mixtures. The second chapter covers methane sampling, which is crucial because many methane explosions have been attributed to sampling deficiencies. Subsequent chapters describe methane control methods for different kinds of mines and mining equipment, primarily for U.S. coal mines. (PDF, 4495 KB, 2006-06)

This Bureau of Mines publication presents investigators' reports of all major coal mine explosion disasters that occurred in the United States from 1959 through November 1981, along with a brief analysis of common factors in these disasters. The report reviews the federal mine health and safety acts of 1969 and 1977, and discusses how implementation of these acts has reduced the number of both fatalities and disasters. Current Bureau health and safety research is summarized, and an appendix lists most of the ignitions and explosions in the period of record. (PDF, 4171 KB, 1983)

This Bureau of Mines report investigates the horizontal trajectory of boreholes drilled in coalbeds using the rotary drilling technique. Test holes drilled in coalbeds showed that the path of a borehole in the horizontal plane depends on drilling assembly configuration, drill bit rotation, and coalbed geologic features. (PDF, 555 KB, 1988)

The U.S. Bureau of Mines has developed an intrinsically safe carbon monoxide (CO) monitoring system for mines by coupling a fiber-optic data telemetry system with a prototype electrochemical CO monitor. (PDF, 1474 KB, 1992)

Coal degasification boreholes drilled from the surface have been successfully hydraulically stimulated to increase the flow of gas from the coal. This Bureau of Mines report describes the hydraulic stimulation procedure for a coalbed, the equipment required, and design criteria for the treatment. Three examples of stimulation treatment show from fivefold to twentyfold increases in gas production. Two sites where the coal was hydraulically stimulated and exposed by subsequent mining show no adverse effect on mining operations through the treated zones. (PDF, 802 KB, 1975)

The Bureau of Mines evaluated the hydraulic stimulation of a gob- degasification borehole to determine if this procedure would aid in degasifying a longwall panel. The stimulated borehole did not degasify the longwall panel as expected either before or after mining of the panel started. It reduced the underground methane emission only 11 pct, considerably less than the reductions effected by two unstimulated boreholes in the same panel. (PDF, 951 KB, 1977)

Research was conducted to investigate how ventilation of a mining face is affected when scrubber flow is greater or less than intake flow. Tests were conducted in a full-scale surface test gallery built to simulate a mining entry with a continuous mining machine at the face. Increasing scrubber flow resulted in lower methane levels even when scrubber flow was much greater than intake flow. (PDF, 846 KB, 1997)

Describes research at a Pittsburgh Coalbed longwall mine to evaluate and optimize bleeder ventilation and gob gas venthole longwall methane control systems. (PDF, 427 KB, 2000)

In this Bureau of Mines investigation, production was monitored for 1 year at over 30 coalbed gas-drainage boreholes located in Alabama, Pennsylvania, and West Virginia. Results indicate that the quality of data gathered from such wells can be improved greatly if potential problems are anticipated and prevented in the early stages of well production.  (PDF, 639 KB, 1978)

Since 1970, abnormally high methane emissions have been observed in eastern sections of the Federal No. 2 Mine operating in the Pittsburgh coalbed in northern West Virginia. The nature and volume of these emissions indicate a source other than the coalbed. An investigation was undertaken to delineate probable methane sources. (PDF, 954 KB, 1984)

The Bureau of Mines preproduction wireless survey system (WSS) and its performance during an in-mine test are discussed in this report. The WSS was developed to reduce downhole surveying time in order to increase the efficiency of drilling long horizontal methane drainage boreholes in coal. Borehole survey data are electromagnetically transmitted from the downhole guidance probe of the WSS, via the drill rod, to the uphole subsystem in less than 1 min per survey transmission, regardless of borehole depth. (PDF, 2550 KB, 1990)

In this report the importance of diffusion in controlling the emission of methane in mines is examined. An in situ diffusion parameter is defined and calculated for a hypothetical unfractured lump of coal in the Pittsburgh and Pocahontas No. 3 Coalbeds. The values obtained are similar to those obtained with lump coal in laboratory experiments. (PDF, 447 KB, 1972)

The Bureau of Mines measured methane emission rates from an advancing salt face ranging from 15 to 56 ft3/ton (0.5 to 1.8 M3/t). Small room size, use of a continuous miner, and a well-defined ventilation system made possible air velocity and methane concentration measurements. These measurements, representing data from 18 production days, were conducted in an area of abnormally low- grade salt. Methane emissions occurred primarily during the advance of the salt face by continuous miner. (PDF, 2100 KB, 1982)

The Bureau of Mines conducted an investigation into the occurrence of outbursts of salt known to be responsible for explosions, fatalities, and damage in domal salt mines. The purpose of the investigation was to develop a basis for predicting these outbursts based on geologic and associated physical properties of salt. The investigation was conducted at the Cote Blanche salt mine in southern Louisiana. (PDF, 1709 KB, 1988)

An investigation of the effectiveness of methane drainage in the lower Sunnyside coalbed at Kaiser Steel Corp. Sunnyside No. 1 Mine in Utah. Most previous attempts to drain methane gas using long horizontal holes were conducted in the eastern coal province. Four degasification holes were drilled from the outside entries of an advancing section. The four holes reduced face emissions by 78 pct. (PDF, 525 KB, 1986)

This report investigates that application of jet fans to ventilate cuts that extend beyond 40 feet. The results of tests involving a jet fan in a 90 foot entry, its benefits and potential problems are discussed. (PDF, 1756 KB, 1992)

This paper addresses the question, 'Can lightning cause potential differences capable of igniting methane-and-air mixtures at overburden depths at which underground coal mining occurs?' (PDF, 614 KB, 2002)

Methane emission from two surface gob-degasification boreholes was measured by the Bureau of Mines. The investigation took place during mining of a 3,200-foot longwall panel in the Lower Kittanning coalbed in central Pennsylvania. The first hole was 500 feet from the start of mining, and the second hole was 2,200 feet. The first hole went on natural draft as soon as the longwall face passed it. This caused the methane flow in the return entries to drop 75 pct. In the 6 months required to complete the panel, the two holes emitted 69 MMcf of methane in varying percentages of concentration in air. In 3 years, the holes emitted a total of 150 MMcf of methane. (PDF, 649 KB, 1976)

Although it is generally believed that coal formation occurred at temperatures below 200 deg c, most experimental work on gas formation from coal has been performed at temperatures between 200 deg and 1,000 deg C. The objective of this Bureau of Mines experiment was to determine if observable changes in the gases from coal could be produced at temperatures below 200 deg c in relatively short periods of time.  (PDF, 1056 KB, 1974)

This chapter summarizes how certain geologic features may be associated with unexpected increases in gas emissions during coal mining. These unexpected emissions have the potential to create explosive conditions in the underground workplace. Also discussed are the generally used practices to alleviate potential hazards caused by gas emissions associated with these geologic features. (PDF, 4851 KB, 2006)

NIOSH research suggest that by incorporating ventilation planning into the mine planning process, using propeller fans, developing new stopping materials and construction methods, and using long pillars to eliminate crosscuts where possible, the ventilation of large-opening mines can be significantly improved. (PDF, 229 KB, 2006-06)

Reports on a test system and computer program developed for using a three-axis ultrasonic anemometer to measure airflow in a simulated mine entry. (PDF, 461 KB, 2004)

The Bureau of Mines and United States Steel Corp. are conducting a joint project to monitor formation pressures at a large (23-well) coalbed gas drainage field near Oak Grove, Alabama. Three monitor holes were drilled in late 1981, and pressure monitoring began in December 1981. The Bureau of Mines direct method was used to obtain gas content data from cores taken in the monitor holes. Comparison of the 1981 gas content data from the monitor holes with initial gas content values obtained from the production wells in 1977 indicates a 50-pct reduction in adsorbed gas content inside the pattern and a 29-pct reduction at one point 500 ft outside the pattern. (PDF, 1492 KB, 1985)

Coalbed gas content measurements are commonly used in mine safety as well as coalbed methane resource assessment and recovery applications. Gas content determination techniques generally fall into two categories: (1) direct methods which actually measure the volume of gas released from a coal sample sealed into a desorption canister and (2) indirect methods based on empirical correlations, or laboratory derived sorption isotherm gas storage capacity data. Direct gas content determination techniques may be further,subdivided into quick-crushing and extended desorption methods. Direct method techniques for gas content measurement are the focus of this paper. (PDF, 1581 KB, 1998-02)

The methane content of virgin bituminous coalbed can now be measured accurately in the field with exploration core samples from vertical boreholes. The gas content of the coal per unit weight can be used either to design a mine ventilation system or to determine if degasification of the coalbed will be necessary before mining, and to determine the gas resources in the coalbed. The equipment necessary to conduct the test costs less than $50. The gas content of the coal in place in the ground is determined by summing the gas lost from coring, gas measured during desorption, and the residual gas in the coal. Friable coals emit nearly 96 pct of the total gas during desorption whereas a blocky coal emits only 60 pct of its total gas. Coalbeds that are ill defined as to their blocky or friable nature must be tested in the laboratory for unambiguous analysis. (PDF, 845 KB, 1975)

The Bureau of Mines made laboratory absorption measurements on oil shale samples, which showed that the amount of methane absorbed is prorportional to pressure and oil yield, and can be much larger than would be predicted based solely on porosity. Oil shale cores collected in the field were also measured for their gas content using the Bureau of Mines direct method. Cores taken from deep locations and far from outcrops yielded more gas than cores from shallower locations or at outcrops, when taking into account variations in oil yield, and all data indicate that oil shale mines that are both deep and far from an outcrop will emit low levels of methane gas. (PDF, 628 KB, 1977)

The Bureau of Mines investigated the presence and extent of methane accumulations in mine roof cavities using a full-scale mine model. Methane was released at a constant rate into the roof of a cavity built onto a 700-ft wind tunnel. Two box-shaped roof cavities were used in the study: one had a volume of 114.7 cu ft; and the other had a volume of 57.3 cu ft. Methane concentration was measured at 28 sampling points in the cavities using 21 different combinations of gas emission rates and air velocities. Brattice hung in the cavity helped reduce methane concentrations without auxiliary ventilation. It was also found that the effective ventilation rate increased by a factor of 40 in the large cavity and by a factor of 20 in the small cavity when air velocity was increased from 100 to 600 ft/min. (PDF, 622 KB, 1978)

The effect of water infusion on the flow of methane and on the production of dust was investigated at an active face in the Pittsburgh coalbed. The average total flow of methane at the face decreased by approximately 79 percent, whereas the flow from the ribs increased about 24 percent after infusion. On the day after infusion, dust concentrations appear to have been reduced; however, the presence of large quantities of rock dust obscured the results on the following days. (PDF, 863 KB, 1972)

The periphery of longwall panels in the Pocahontas No. 3 Coalbed is characterized by a zone of reduced permeability that inhibits the natural drainage of methane. However, natural drainage holes drilled during development have been found to reduce the gas content of the coal in this coalbed by over 90 percent. The effect of water infusion on dust during plowing operations was investigated using existing methane drainage holes. Both total and respirable dust levels were reduced by 40 to 79 percent. Water infusion of the panel proved more effective than did the use of a plow-mounted spray system. (PDF, 1130 KB, 1974)

The Bureau of Mines developed data on the methane content of the Hartshorne coalbed, Haskell and Le Flore Counties, Oklahoma. The methane content is calculated to be between 1.1 and 1.5 trillion cubic feet. Methane increases with depth, but the rate of increase decreases with greater depths. Degasification in advance of mining is recommended for all mines operating at depths greater than 500 feet to reduce hazards and methane explosions, decrease mine ventilation costs, and conserve the natural gas that would be otherwise wasted. (PDF, 1104 KB, 1979)

The Bureau of Mines determined the gas contents of 135 oil shale samples obtained from approximately 630 ft of core drilling. Drilling was done within a projected mining zone of the Cathedral Bluffs Mine, located in the Piceance basin of western Colorado. Methane contents were determined by the modified direct method, which can measure the volumes of several gases released from or reacted with mine rock without destructive sample treatment. (PDF, 2039 KB, 1987)

This chapter gives guidelines for preventing methane gas explosions at continuous miner sections in coal mines, both at continuous miners and at roof bolters. The need to control peak methane emissions is particularly stressed. Emphasis is also placed on ventilation principles, monitoring for gas, and reducing frictional ignitions. (PDF, 4851 KB, 2006)

As one of its projects for degasification of major panels of coal prior to mining within them, the Bureau of Mines conducted methane emission studies during development of a set of three headings 1,800 feet in a major coal panel (2,700 by 3,500 feet) which had been completely isolated by sets of main headings for 12 months in the Federal No. 2 Mine (Pittsburgh coalbed) in northern West Virginia. Similar emission studies were conducted in the development of two sets of main headings in virgin coal areas nearby. Comparing the two sets of data indicated that the isolated coal panel had been degasified by approximately 70 percent. (PDF, 497 KB, 1973)

Ventilation has long been the primary means of controlling methane emissions in underground coal mines. However, as mining has progressed into gassier areas of U.S. coal basins, supplemental means of methane control have become of interest, if not a necessity, for continued safe and productive mining operations. This paper describes the history and technology of methane drainage in the United States and other countries. The methane drainage technology developed in European countries is a valuable resource since their longer history of mining has already forced mine operators to deal with methane emission problems only now being experienced in the United States. (PDF, 3232 KB, 1994)

Research workers from the Bureau of Mines and industry met with other government and industry representatives at the Mont Chateau Lodge, Morgantown, West Virginia, on May 30-31, 1973, to discuss the current status of methane control in eastern U.S. coal mines. The opening remarks, the eight technical presentations, and the discussions of the members of a government-industry panel are published here for the benefit of those concerned with the control of methane in coal mines. (PDF, 8521 KB, 1973)

Presents a brief summary of the explosion trends in United States coal mines for the past 160 years. These trends show that in spite of the overall improvements in mine safety, the number of fatalities from ignitions of methane has actually increased in recent years. Suggestions are made of procedures that can be utilized to reverse this trend. (PDF, 1249 KB, 1973)

The cross-measure borehole technique is an effective method of controlling methane liberated by fracturing the roof strata in longwall gobs where overburden is less than 750 ft (229 m). About 71 pct of the methane produced by longwall mining in the Lower Kittaning coalbed was captured by the cross-measure boreholes. Borehole spacing is an important factor affecting the performance of the technique. (PDF, 1188 KB, 1985)

A sorption apparatus for measuring the equilibrium sorption isotherm and the rate of diffusion of methane from fine-sized coal was designed and constructed. Preliminary work that used Pittsburgh and Pocahontas No. 3 Coal shows that the diffusion coefficient varies with pressure and that the fracture spacing in these two coals is substantially different. (PDF, 618 KB, 1972)

Discusses research to determine the effectiveness of long holes in degasifying an area of the upper split of the lower Sunnyside coalbed at Kaiser SteelCompany Sunnyside No. 1 mine. These holes were drilled from the two outside entries of a section that was closed to mining because of excessive methane emissions. Two holes drilled to 430 and 450 feet eventually reduced face emissions by about 40 pct. (PDF, 851 KB, 1978)

The Bureau of Mines has completed an underground degasification project in which an underground piping system was used to transport methane from the coalbed to the surface. In a 10-month period four horizontal holes were drilled to an average depth of 1,450 feet. The underground piping system proved to be a safe and effective means of transporting methane from the coalbed to the surface. (PDF, 3837 KB, 1981)

The Bureau of Mines examined the wellbore of a vertical gas drainage well in the Mary Lee coalbed to determine the results of specific completion procedures in coal. A jet-slotting tool was used to cut four vertical slots through the casing about 1 ft below the coalbed. Even though stimulation treatment pressure was excessive, hydraulically induced channels were contained entirely within the target coal zone. Sand-filled, induced channels were horizontal, inclined, and vertical, and were propagated in directions similar to bedding planes, rock joint, and coal cleat directions measured in the mine. Variable gas flow rates, recorded during the productive life of the well, were attributed to chronic downhole pump malfunction and the slotted casing below the production zone. (PDF, 858 KB, 1978)

This Bureau of Mines survey of methane emissions indicates that total daily emissions have declined from 227 mm ft3 in 1971 to 214.7 mm ft3 in 1973. The highest average daily emissions in million cubic feet per day are detailed by state. (PDF, 1562 KB, 1974)

This Bureau of Mines report tabulates methane emissions from U.S. Bituminous coal mines with daily emission rates of at least 100,000 cfd according to states, counties, and coalbeds. Most of the methane emitted is from mines in the Appalachian States. Thirty counties in nine states had daily methane emissions of 1 MMCFD or more. These emitted 93 percent of the total methane. The report lists 196 mines, of which 60 had daily methane emissions of 1 MMCFD or more. Included in this compilation are the identification and thickness of the coalbed, methane emission, coal production and ventilation rates, number of drifts, shafts, and slopes used for ventilation purposes, shaft depth, age of mine, and gas-to-coal ratio. (PDF, 1915 KB, 1977)

This survey was conducted to determine the magnitude of the methane emission and control problem in U.S. bituminous coal mines. The resultant data indicate that the emission rate for any given coalbed depends primarily on the coal production rate and on mine depth, as well as on the nature of the coalbed and the surrounding strata. An excellent correlation was found between (1) the methane emission rate and (2) the product of coal production rate and mine depth for area mines. (PDF, 3003 KB, 1972)

The method of moving averages was found useful in assessing the nature of methane emission in coal mines. Emission rates were influenced markedly by the presence of abandoned oil and gas wells in the vicinity of the mine. Such wells appeared to increase the flow rate of methane into the mine by a factor of 2 to 30 in an active mine in the Pittsburgh coal seam. (PDF, 2665 KB, 1972)

The purpose of this study was to determine the characteristics of methane emissions during coal extraction by a longwall mining system. The study was conducted over 22 consecutive shifts. The average methane emission rate from the Lower Kittanning coalbed during mining at the face and developing the headings at the tail end of the face was 34 cfm. Caving of the gassy overlying strata as the result of mining at the face increased the methane emission to rates ranging from 702 to 1,049 cfm. (PDF, 656 KB, 1971)

Methane emission rates were studied in a Pittsburgh coalbed mine in northern West Virginia. Air volumes and methane percentages were recorded, and time studies of the miner were made during five consecutive operating days, during which a complete cycle of mining the headings and one line of related breakthroughs was accomplished. (PDF, 780 KB, 1970)

A degasification experiment was conducted in a Pocahontas No. 3 Coalbed mine in Virginia. It involved (1) drilling holes in the coalbed in the outside headings of a set of five being developed in virgin area and (2) conducting a methane emission rate study as mining progressed and additional holes were drilled. Degasification from all drill holes except the longest in each of the outside headings and the first three drilled (excluding the in situ pressure hole) was erratic and inconsequential in methane emission rates. The two longest holes liberated 66 and 79 cfm of methane, which is significant for the coalbed, but such quantity lasted a relatively short time; the first three were uniform but low in methane emission. (PDF, 688 KB, 1972)

The methane emissions from an advancing coal mine section were continuously monitored for 120 days. During this time, the section advanced 2,000 feet into virgin Pittsburgh coalbed producing 54,565 tons of coal with a total methane emission of 91 million ft3. Analysis of the data gathered showed that daily methane emissions did not correlate with overburden thickness and daily coal production. A good correlation was found between the daily methane emission and the average length of rib exposed to virgin coal. (PDF, 444 KB, 1976)

The Beckley Mine is one of five new mines in a heretofore unmined portion of the Beckley coalbed. The remoteness of these new mines from prior mining and their greater overburden preclude applying methane emission experience obtained in the old mines. Four sections of the Beckley Mine were monitored. The data gathered show that variations in methane emission cannot be explained by variations in coal production. Although overburdens varied by as much as 30 pct, no correlation with methane emissions could be determined. The rib emissions increase with increased length of rib from a section advancing into virgin coal and do not decline over a prolonged idle period (32 days) whereas some decline has been measured for a section not mining into virgin coal. The indication is that degasification prior to mining will reduce the hazard of methane emissions in this area of the Beckley coalbed. (PDF, 526 KB, 1977)

The methane gas emitted from coal samples collected from the conveyor belts dumping into silos was measured. Approximately 50 pct of the total gas desorbed into a sealed can within 1 week was released during the first 24 hours. No simple correlation between the gassiness of the coal stored and the methane concentration in the silo open space above the coal was found. This was probably because the gassier coals were stored in open-top silos, which were better ventilated. Although the methane concentration in the open space above the coal pile was less than 1 pct for all 34 silos investigated, a methane measurement in the coal pile showed that high methane concentrations can exist. The methane released in the pile appears to accumulate and not liberate freely into the open space above the coal pile. Probably this gas is released during reclaiming operations, but further research is required to substantiate this claim. (PDF, 583 KB, 1978)

A tabulation of methane emissions during 1980 for all United States coal mines with emissions greater than 0.1 MMcfd. The report also compares records of 1975 and 1980 and describes relationships between emissions in 1980 and the Bureau's coalbed gas content data on 11 mines. (PDF, 1325 KB, 1984)

It is estimated that more than 1 trillion cubic feet of methane is contained within the coals of the Mary Lee Group in Jefferson, eastern Tuscaloosa, and southern Walker Counties, Alabama. It is calculated that approximately 90 pct of the methane is at depths greater than 1,000 feet, and over half is contained under more than 1,500 feet of overburden. Degasification in advance of mining will increase mine safety, reduce ventilation expenditures, increase productivity, provide an additional energy source, and make it possible to mine parts of deep coalbeds that probably could not otherwise be mined. (PDF, 465 KB, 1976)

Methane flows and pressures were measured in mines in the Pittsburgh, Hartshorne, and Pocahontas No. 3 Coalbeds. From the data, the permeability of each of these coalbeds was computed. (PDF, 756 KB, 1972)

Methane-flow and pressure data taken from a mine in the Pocahontas No. 3 Coalbed are compared with flow rates from lump coal obtained in laboratory experiments. From this, it is concluded that the main source of gas is the intact coalbed rather than a "crushed zone" near the working face. The permeability and sorption capacity of the intact coalbed are calculated and gas emission rates are theoretically accounted for. (PDF, 714 KB, 1972)

Researchers conducted experiments to estimate the mean and standard deviation of laser powers needed to ignite 6% methane-air atmospheres using single mode optical fiber tips covered by two types of iron oxide (Fe3O4 and (FeMn)(2)O-3) mixed with a ceramic adhesive. (PDF, 2042 KB, 2006-09)

Gob holes are routinely used by the mining industry to vent methane from gobs and to prevent it from entering the mine ventilation system. In some cases, flows from gob holes are measured by centering an anemometer on the end of a discharge pipe. These measurements are erroneous and tend to be high by as much as 30 pct. The Bureau of Mines determined method factors (correction factors) for anemometer measurements taken in this manner. (PDF, 1040 KB, 1987)

The U.S. Bureau of Mines investigated a method of using inert gas to prevent the formation of explosive gas mixtures in auger highwall mining of coal. A combination of gasoline and diesel engine exhaust gases was introduced into the auger drill hole using a short section of pipe located at the collar. (PDF, 3723 KB, 1993)

Methane can be a significant hazard in coal mine longwalling operations and extensive methane mitigation techniques are employed by coal mine operators. Reservoir modeling techniques are used to better understand the liberation and migration of methane from the surrounding rocks towards the mine ventilation system. The caved rock behind the advancing longwall face, known as the gob, can contain high void ratios, providing high permeability flow paths to the methane. The gob is progressively compacted by the weight of the overburden, resulting in a reduction in the void ratio and associated permeability. Estimating the permeability distribution within the gob poses challenges due to its complexity. The authors have developed a new methodology to determine both horizontal and vertical variations in the permeability of the gob. The resulting three-dimensional permeability distribution in the gob is then transferred to a reservoir model. The paper demonstrates the application of the method and shows that reasonable results are obtained when compared to empirical experience and measurements. (PDF, 1146 KB, 2007)

The Bureau of Mines has developed two experimental designs for determining the volumes and relative proportions of the various gas species, particularly methane (CH4), occluded in rock salt. The two methods are ball- mill crushing and dissolution. Of the two, the dissolution method appears to be more versatile because it can be performed in situ. The relevance and applicability of data on the occluded gas contents of rock salt are dependent on sample size, sample collection method, geologic context of the sample, and the correlation with gas emissions that occur as a result of mining-induced fractures and pressure differentials. (PDF, 651 KB, 1982)

At coal mine working faces, simultaneous application of three basic elements reduces the methane explosion hazard: (1) adequate ventilation, (2) regular monitoring of gas concentrations, and (3) the elimination of ignition sources. This paper reviews the application of these elements in a manner relevant to Chinese coal mines. (PDF, 242 KB, 2007)

Large-scale explosion tests conducted within the multiple-entry section of NIOSH's Lake Lynn Experimental Mine (LLEM) are currently the only accepted test method for deeming a seal design suitable for use in U.S. mines. These explosion tests are labor-intensive, expensive, and can interfere with other critical underground safety and health research programs. NIOSH has developed an alternative seal evaluation method, based on a hydrostatic pressure-loading concept, that can facilitate the in situ testing of seals in an operating mine. This approach also allows for the determination of the seal's ultimate design strength. (PDF, 1046 KB, 2005)

This paper serves as an overview to remind and/or instruct readers about gas-sampling methodologies and gas analyses to assist in determining the status of underground atmospheres. (PDF, 173 KB, 2006)

This paper serves as an overview to remind and/or instruct readers about gas-sampling methodologies and gas analyses to assist in determining the status of underground atmospheres. (PDF, 158 KB, 2006)

MFIRE is a computer simulation program that performs normal ventilation network planning calculations, and dynamic transient state simulation of ventilation networks under a variety of conditions. This user manual describes the development of MFIRE, the input format and requirements, the output, common errors, fire parameters, and examples MFIRE application. (PDF, 968 KB, 1995-08)

To transfer CFD expertise to analyze and design a face-ventilation system, a comprehensive validation study of current CFD tools against mining-related benchmark experiments is required. This study was dedicated to the methane behavior in an empty (containing no equipment) face area with a blowing curtain and a 10.7-m (35-ft) setback. The authors present and discuss computer-simulation data and compare them with data collected during laboratory studies of current CFD tools against mining-related benchmark experiments at the NIOSH lab. (PDF, 707 KB, 2007-10)

This study proposes a principle component analysis (PCA) and artificial neural network (ANN)-based approach to predict the ventilation methane emission rates of U.S. longwall mines. (PDF, 844 KB, 2008-02)

This paper covers the development of NIOSH's modified direct method to measure the gas content of coal samples. (PDF, 158 KB, 2001)
                                        

This work by NIOSH has modelled the impacts of borehole pattern and design and the effects of increasing face length on gob gas venthole performance. (PDF, 261 KB, 2008)

The Super Stopping is designed as a long-term permanent stopping for use in the main entries of the mine, while the EZ-Up Curtain Stopping, although very durable, is designed more for portability and ease of installation. This paper describes the design, materials, and construction methods used for these stoppings, as well as their performance and durability when subjected to tests simulating actual production face blast pressures. (PDF, 202 KB, 2006-06)

NIOSH has initiated a reservoir modeling effort to better understand the interaction of the various geotechnical factors influencing gas flow within and to the underground longwall mining environment. A focus of this modeling effort has been (1) the prediction of the incremental amount of methane emissions to be expected due to increasing longwall panel widths and (2) optimizing gob gas venthole completion practices to capture more of the gas in the subsided strata above longwall panels before it can enter the ventilation system of the underground workplace. (PDF, 353 KB, 2005)

This study investigates different horizontal methane drainage borehole patterns, borehole lengths, and degasification times prior to and during panel extraction to evaluate their effectiveness in reducing methane emissions using a dynamic 3D reservoir modeling of a 381-m wide longwall panel operating in the Pittsburgh coalbed. (PDF, 1223 KB, 2007-09)

This study uses reservoir simulations to illustrate the effects of impermeable faults, with and without throws, on the production performance of vertical and horizontal degasification boreholes and presents the effects and the impacts of impermeable faults on methane emissions due to an advancing coal face. (PDF, 1527 KB, 2008-09)

Many mines rely on toxic gas sensors to help maintain a safe and healthy work environment. This report describes a prototype monitoring system developed by the U.S. Bureau of Mines (USBM) that uses light to power and communicate with several remote toxic gas sensors. (PDF, 1565 KB, 1995)

Provides information on the explosibility and ignitability properties of dust clouds that can be used to improve safety in industries that generate, process, use, or transport combustible dusts. (PDF, 583 KB, 2000-05)

Methane concentration peaks were measured at coal mine working faces during entry development. The statistical distribution of peaks was found to be normal or log normal depending on how well the methane was being mixed into the ventilation airstream. A normal distribution indicated good mixing, whereas a log-normal distribution indicated that mixing was poor. The "highest" peaks over selected intervals were found to fit a type I extreme-value distribution, a result similar to that obtained while mining longwall faces. (PDF, 604 KB, 1974)

This paper presents the results of the full-scale test of a composite polyurethane-aggregate seal in a hydrostatic chamber conducted by NIOSH Pittsburgh Research Laboratory at the Lake Lynn Experimental Mine, and provides an analysis of those results in terms of the structural behavior of the seal. (PDF, 2963 KB, 2008-05)

The Pittsburgh Research Laboratory (PRL) of NIOSH and the Mine Safety and Health Administration (MSHA) conducted joint research on dust explosions by studying post-explosion dust samples. All these data will be useful in future forensic investigations of accidental dust explosions in coal mines, or elsewhere. (PDF, 760 KB, 2007-07)

NIOSH and MSHA conducted joint research on dust explosions by studying post-explosion dust samples. The samples were collected after full-scale explosions at the PRL Lake Lynn Experimental Mine and after laboratory explosions in the PRL 20-L chamber and the Fike 1 -m3 chamber. The dusts studied included both high and low volatile bituminous coals. (PDF, 1164 KB, 2006)

Overview of a variety of techniques and methods that can be used to improve the air quality in underground stone mines. (PDF, 1680 KB, 2002-10)
                                

NIOSH conducted a longwall methane emission and mining time study at a mine in the Pittsburgh Coalbed to access the methane emission consequences of mining a longer face. Based on the results, site-specific mathematical formulas and constants were developed to characterize four longwall emission contributors. The formulas were then applied to longer longwall face mining scenarios to predict methane emissions from these faces. (PDF, 186 KB, 2006-06)

An analysis of the consequences of increasing longwall panel dimensions, particularly face width, in gassy coalbeds. Continuous longwall face emission monitoring studies were conducted at two adjacent mines operating in the Pocahontas No. 3 Coalbed, where longwall faces were to be extended from 229 to 305 m (750 to 1,000 ft). (PDF, 1840 KB, 1999)

NIOSH conducted a study to characterize and quantify the methane emissions resulting from increasing face lengths in the Pittsburgh Coalbed. The goal was to provide the mine operator with a method to predict the increase in methane emissions from the longer faces for incorporation of additional methane control capacity into the mine planning process, if necessary.  (PDF, 176 KB, 2006-06)

The U.S. Bureau of Mines and the United States Steel Corporation evaluated the progress of methane drainage at the Oak Grove, Alabama, degasification pattern. Coalbed pressures were monitored between December 1981 and November 1985. The effect of the advance of a section of the Oak Grove Mine on changes in gas and water production rates in the pattern was evaluated. (PDF, 1570 KB, 1989)

Probabilities of encountering coalbed discontinuities during vertical or horizontal drilling in a specific coalbed can be estimated based on analysis of mined-out areas of the coalbed where the size, shape, orientation, and distribution of discontinuities are known. The resultant probability estimates can be applied to cost-risk evaluations of drilling programs proposed for exploratory, developmental, or methane drainage purposes in undeveloped areas of that coalbed.  (PDF, 1160 KB, 1982)

Major problems facing the development of coal and gas resources of the Hartshorne Coalbeds include the complex distribution of minable and unminable coal, high methane content and bed pressure, faulting, variations in degree of dip, presence of natural gas fields in assocated sandstones, and legal problems, caused by local geologic characteristics, in identifying gas origin. This study provides pertinent geologic information for long-range planning of subsurface coal and gas production from the Hartshorne Coalbeds. (PDF, 1898 KB, 1983)

Describes the results of a case study where NIOSH demonstrates that significant increases in total mine airflow can be achieved and the ventilation improved in a large-opening stone mine by replacing an axial-vane mine fan with two 12-ft diameter propeller fans and adding a line of stoppings. (PDF, 420 KB, 2004)

The Bureau of Mines has developed a system using a high-speed electropneumatic mechanism for the rapid (grab) sampling of dusts and gases during an explosion. The sampling system consists of an aluminum housing that incorporates two 30-cm3 preevacuated glass vials with rubber septums. Upon actuation, the sampling probe needle is driven through the septum with a pressurized air pulse, filling the tube with gas and dust from the mine explosion. (PDF, 3254 KB, 1988)

This paper describes a U.S. Bureau of Mines investigation of large-scale coal dust explosions in an experimental mine using a high speed electropneumatic mechanism for the rapid grab-sampling of gases and dusts. This technique enables the monitoring of pyrolysis and charring in fuel dust particles, and the collection of gaseous combustion products, in both large and small-scale explosions. (PDF, 1576 KB, 1991-02)

This paper briefly describes the progress in mine safety in the United States, with emphasis on recent events that have followed since the explosion at the Sago Mine in January 2006. Legislation following the mine accidents in 2006 and areas of work carried out by NIOSH related to the accidents are discussed. (PDF, 3543 KB, 2007)

Criteria were documented for the recognition and prediction of discontinuities in advance of mining. (PDF, 2448 KB, 1985)
                                                   

Reports on the U.S. Bureau of Mines development and testing of an instrinsically safe methane monitor based on differential absorption of infrared light. (PDF, 1160 KB, 1992)

Report on the development and field testing of a solar powered, remote gob gas venthole monitoring and cellular telephone-based real-time data transmission system. (PDF, 844 KB, 2002-10)

A joint investigation by the Bureau of Mines and the Christopher Coal Co. at the Humphrey No. 7 mine, operating in the Pittsburgh coalbed in northern West Virginia, was undertaken to gain more insight concerning the hazardous emission of methane gas in mining. This report describes the equipment, procedure, and results.  (PDF, 3221 KB, 1962)

Tests were conducted in the Pocahontas No. 4 coalbed in southern West Virginia to determine if successful degasification techniques, developed during an earlier study in the Pittsburgh coalbed, would effectively remove methane from those usually more gaseous coals. Infusions were made with water at normal waterline pressures ranging from 200 to 220 psi or at pump pressures ranging from 400 to 650 psi, Methane emissions from free-flow bleeder holes were as much as 131 cfm. Infusions of some of the holes increased the methane emission from other holes and from the exposed coal surfaces near the working areas as much as 1,540 cfm. The methane content in the main return air currents after infusion was reduced more than 86 percent. (PDF, 2399 KB, 1963)

The importance of controlling respirable dust and methane gas levels in underground coal mining cannot be underestimated. While respirable dust can significantly affect the occupational health of underground coal miner, methane gas accumulations pose significant safety concerns for these same workers. (PDF, 263 KB, 2001)

This NIOSH study presents an approach for prediction of methane inflow rates using coalbed methane reservoir modeling which can be used to limit the methane concentrations occurring as a result of the influences of various coalbed and operational parameters.  (PDF, 146 KB, 2008)

This study presents reservoir and elastic properties of coal measure rocks in the Lower Monongahela Group in Greene County, southwestern Pennsylvania, of the Northern Appalachian Basin. The results presented in this study can be used as data sources for reservoir studies related to the production and control of methane. (PDF, 1922 KB, 2009-03)

This paper presents the development and results of a comprehensive, "dynamic," three-dimensional reservoir model of a typical multi-panel Pittsburgh coalbed longwall mine. Results presented in this paper include a simulation of gas flow patterns from the gas-bearing zones in the overlying strata to the mine environment, as well as the influence of completion practices on optimizing gas production from gob gas ventholes. (PDF, 2787 KB, 2007-07)

This report presents a data base of gas content data. The data are presented in tabular form, by coalbed name and state. The components of the total gas content (lost, desorbed, and residual gas) are given. Location (state and county), sample depth, coalbed or formation name, and coal rank are included for geographic and geology identification. Combined with geologic and engineering studies, these data can be used as a basis for a preliminary estimate of mine ventilation requirements, and to determine whether methane drainage in advance of mining should be considered. (PDF, 4676 KB, 1986)

Laboratory and field tests of vane axial main mine fans in the 7- to 9-ft diameter size range were conducted to establish forward and reverse performance characteristics under controlled conditions and at typical mine installations. (PDF, 1655 KB, 1983-08)

Reviews underground methane drainage programs being conducted in various coalbeds. Equipment used in drainage programs such as drills, underground pipelines, and methane monitoring systems is described. (PDF, 3091 KB, 1980)

Outbursts are sudden and violent releases of gas and coal that result from a complex function of geology, stress regime, and gas pressure and content. The Bureau of Mines has reviewed methods for prediction and mitigation of such outbursts in use worldwide as an aid in selecting the proper techniques for use in specific mine environments. (PDF, 681 KB, 1987)

This paper highlights some of the widely used standards for accurate flammability and ignitability data for chemicals, complemented with hypothetical but relevant examples describing the testing strategy, interpretation, and application of the results.  (PDF, 310 KB, 2005)

Coal is a soft and brittle material. Drilling rates in the Pittsburgh coalbed using a drag bit exceed 3 ft/min at 2,500-pound thrust. However, maintaining the bit on a horizontal trajectory or parallel to bedding planes to attain lengths of 1,000 feet is difficult. This Bureau of Mines report presents a drill string configuration that can be guided through the coalbed. (PDF, 1730 KB, 1975)

The U.S. Bureau of Mines used a contact drilling strategy with short-collared assemblies in order to rotary drill long horizontal methane drainage holes in the Beckley coalbed near Glen Daniel, West Virginia. By decreasing the thrust and increasing the rotation of the drill bit when in contact with the roof and floor rock, assemblies were made to deflect and stay in the coalbed. Successful application of this procedure resulted in holes drilled full length in coal with the original assembly including bit. (PDF, 952 KB, 1989)

The roles of main mine fans in underground mines are to induce airflow and continuously remove hazardous gases and dust. While most larger mines use multiple fans to accomplish these tasks, many smaller mines employ only a single fan. This paper concentrates on those mines having only one fan to provide ventilation needs. (PDF, 372 KB, 2002)

As the use of deep-cut mining increases, there is expected to be a greater demand for methane measurement devices capable of scanning working faces at depths in excess of 10 m to alert mine personnel of hazardous concentrations of methane and to satisfy regulatory requirements. A second-generation remote optical methanometer has been designed and is undergoing laboratory evaluation at the National Institute for Occupational Safety and Health. (PDF, 355 KB, 1997)

As part of the Bureau of Mines methane control program, the Pittsburgh coalbed was studied in Washington and Greene Counties, Pennsylvania, and in Marion and Monongalia Counties, West Virginia, where this coalbed is now being mined at its greatest depth. The results of these investigations provide a geologic framework for rational planning for underground mine development to use the best available technology to cope with methane emissions, coalbed discontinuities, and related ground support problems.  (PDF, 3764 KB, 1975)

Various silicone materials have been proposed for use in mining environments. The catalytic methane sensors now employed are poisoned by silicone vapors. Activated charcoal and carbon cloth adsorbents will increase the sensor lifetimes in an environment containing significant silicone vapor concentrations. The results of a study of catalytic methane sensor operation with adsorbent materials in hexamethyldisiloxane-air mixtures are reported. Sampling techniques developed for measuring silicone vapor content of mine atmospheres are described. (PDF, 2381 KB, 1978-10)

The Bureau of Mines has successfully tested a method to simulate methane (CH4) flows from face areas through the returns of noncoal mines. This technique involves releasing a small quantity of tracer gas at a working area and sampling for that gas downstream in the return airways. By measuring the dilution of the tracer gas, the dilution of any volume of CH4 released at the face can be calculated. This information is useful in selecting locations for CH4 monitors and in deciding the necessity for permissible equipment in the returns. (PDF, 540 KB, 1984)

The objective of this paper is to provide information on specific geologic factors that should be considered prior to, during, and after the drilling of coalbed gas drainage boreholes. Many of the commonsense considerations that have been learned through many years of Bureau of Mines experience, but have generally not been reported formally, are included. (PDF, 1601 KB, 1982)

The Bureau of Mines has conducted desorption work on fine coal particles at near atmospheric pressure. An apparatus has been developed that uses a capacitance manometer to measure desorption of methane from coal particles up to 2 inches in diameter and pressures up to 1,000 psi. This will make it possible to duplicate the desorption process as it occurs in its natural underground environment.  (PDF, 985 KB, 1969)

This report is a summary of the work accomplished during the performance of the project titled "Specialized Fortran Computer Programming and Analysis Services to Upgrade Capability of MFIRE Program". This project investigated and corrected algorithm convergence errors in MFIRE versions 1.29 (for dry case) and 2.01/2.0 (for both dry and wet cases), resulting in MFIRE software upgrades 1.30 and 2.10, respectively. (PDF, 19078 KB, 1994-12)

During the normal course of underground coal mining, it sometimes becomes necessary to seal off abandoned areas to eliminate the need to ventilate them. Seals also are used to isolate fire zones or areas susceptible to spontaneous combustion. The objective of the research is to determine whether seals constructed from various materials and designs can withstand a 20-psig methane-air explosion without losing their structural integrity. (PDF, 2326 KB, 1993)

This report discusses the testing and full-scale evaluations of a recently developed carbon fiber-reinforced polymer (CFRP) reinforcement technique for upgrading existing mine ventilation seals to withstand an explosion pressure of 50 psi or greater which were conducted in the NIOSH Pittsburgh Research Laboratory´s Lake Lynn Experimental Mine (LLEM) near Fairchance, PA. (PDF, 7610 KB, 2008-01)

An existing computer program for mine ventilation network is modified so that it can simulate ventilation conditions under the influence of mine fires. The resulting new program is designed for the practical ventilation engineer and should be applicable to all types of ventilation emergency plans, in particular mine fire plans. The organization of the program and its mathematical basis are described. (PDF, 21500 KB, 1977-09)

This paper describes the effect of machine-mounted dust scrubbers on the performance of face ventilation systems using extended-cut mining with a blowing curtain. (PDF, 307 KB, 2008)

Sulfur hexafluoride (SF6) is an odorless, colorless, nontoxic gas that has found acceptance as a tracer gas in research on ventilation patterns, measurement of air leak rates, respirable dust reductions due to bagging hood modifications, and the study of airflows relating to gob boreholes. Following a short review of the SF6 sampling technique, this report describes recent Bureau of Mines projects in which SF6 was used successfully as a tracer gas, enabling researchers to acquire representative data quickly and inexpensively. (PDF, 1374 KB, 1982)

This paper discusses the spatio-temporal volumetric strains in a consolidated Pittsburgh seam coal sample which were evaluated while both confining pressure and carbon dioxide CO₂ pore pressure were evaluated.  (PDF, 1547 KB, 2007-11)

The NIOSH Pittsburgh Research Laboratory, in collaboration with MSHA Technical Support, has devised a prototype handheld instrument that can provide a direct assessment of the potential explosibility of a coal and rock dust mixture. The Coal Dust Explosibility Meter (CDEM) is not intended to replace the current MSHA laboratory analysis of coal mine dust samples for incombustible content, but rather to serve as a supplemental device for enhancing mine safety through improved rock dusting practices. (PDF, 145 KB, 2006)

The objective was to develop and demonstrate a lightweight material that has low thermal conductivity and that would be suitable for placement using shotcrete methods. This material could be applied in deep, hot mines where mine drifts must be insulated. Its use would decrease mine refrigeration needs and reduce energy costs. (PDF, 90 KB, 1994-05)

This Tech News reports on the successful application of total mill ventilation systems to reduce respirable dust concentrations and comply with federal regulations regarding respirable dust (PDF, 66 KB, 1994-05)

The absence of fundamental scientific and engineering principles in the design and placement of gob gas ventholes can cause difficulties for mine operators when gas emissions increase because of a change in mine design or because variable geologic conditions are encountered. (PDF, 64 KB, 1995-03)

This Tech News reports on the evaluation of the air quantity reaching the face of a 40 foot box cut during a two-pass extended cut sequence. (PDF, 56 KB, 1998-05)

Discusses one type of explosion hazard that was discovered lurking inside sealed and filled plow frame sections when NIOSH investigated ignition incidents resulting from drilling into plow frames. (PDF, 69 KB, 1998-06)

An apparatus is described that advances the state of the art in gas content testing of coal or rock core samples. The design goals were to improve sensitivity/accuracy, durability, and ease of operation. (PDF, 56 KB, 1999-08)

Techniques are identified to reduce the probability of gob gas explosions. (PDF, 536 KB, 2001-05)
                                                                             

Description of a passive, inexpensive technique for monitoring explosion overpressures within sealed areas in underground coal mines. (PDF, 288 KB, 2001-06)

This Tech News reports on how the use of propeller fans can significantly improve the ventilation in large entry stone mines due to their efficiency at lower pressures and less required horsepower. (PDF, 152 KB, 2002-12)

The growing realization of the importance of a healthy work environment along with increased regulations will require many stone mines to implement new ways to improve ventilation. In-place stone stoppings are one option. (PDF, 152 KB, 2002-12)

Conventional anemometers (e.g., vane) are capable of accurately measuring air velocities only above 100 ft/min. This research investigated other anemometry technology to detect low air velocities in the range of 0-100 ft/min. Two different portable ultrasonic anemometers were tested in an underground limestone mine with openings about 51 ft wide by 29 ft high. (PDF, 385 KB, 2003)

In underground coal mining, dust is produced at the face, at conveyors, at transfer points, and by the normal movement of workers and machines. The coarse coal dust particles settle rapidly. However, the fine coal particles remain airborne much longer, and the ventilating air can move this fine dust relatively long distances into the returns before settling. This fine dust is called float coal dust. It generally consists of particles of coal that pass a 200-mesh sieve (particles smaller than 75 micrometers). Generalized rock dusting is currently the primary means of defense against coal dust explosions in U.S. mines. 30 CFR 75, Subpart E (Combustible Materials and Rock Dusting), requires the use of rock dust in bituminous coal mines (30 CFR 75.402). The regulations state that rock dust shall be distributed upon the top, floor, and sides of all underground areas of a coal mine in such quantities that the incombustible content of the combined coal dust, rock dust, and other dust shall be not less than 65%, and the incombustible content in the return air courses (where the dust is expected to be finer) shall be no less than 80% (30 CFR 75.403). These incombustible concentrations assume that the coal and rock dust are not layered, but are intimately mixed. Float coal dust is a serious explosion hazard if it accumulates on top of the rock dust and is not mixed thoroughly with the rock dust. (PDF, 663 KB, 2006-04)

The Super Stopping is a permanent, long-term ventilation control for large-opening metal/nonmetal mines designed to last for the life of the mine. This report discusses construction of a Super Stopping, as well as successful testing of the stopping at 3psig blast pressure from an unconfined explosive charge at NIOSH's Lake Lynn Laboratory. (PDF, 77 KB, 2006-05)

The EZ-Up curtain stopping is designed primarily for use as a temporary or portable stopping, although test results indicate that it may remain durable for an extended time. It can be constructed from a variety of fabrics, including standard mine brattice. Stoppings composed of two separate curtain materials were evaluated: (1) a high-density polyethylene woven fabric and (2) a string-reinforced polyethylene film and polyester fabric. Both remained intact after being subjected to a maximum 3psig blast pressure. (PDF, 82 KB, 2006-05)

This briefly describes testing done to ignite methane-air in the presence of liquid hydrocarbons, and gives recommendations for limiting fricitonal ignition. (PDF, 194 KB, 2008-03)

The use of vertical surface degasification boreholes with bleeder systems and the use of a timbered bleeder system to degasify gob areas were studied by the Bureau of Mines. This report describes three gob degasification studies conducted in the Pittsburgh coalbed. (PDF, 838 KB, 1980)

This report describes three coal mine ventilation studies by the Bureau of Mines in which sulfur hexafluoride (SF6) was used as a tracer gas. One study was conducted to determine air movement and leakage in a sealed area. Another was run to determine the ventilation efficiency of a bleeder system. Finally, a study was made of air leakage across permanent stoppings of parallel intake airways. These studies proved sulfur hexafluoride to be a useful addition to the equipment commonly used in coal mine ventilation analysis. (PDF, 848 KB, 1976)

The National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory conducted a study of laser safety in potentially flammable environments. Researchers measured threshold igniting powers as a function of beam diameter for butane and propane-air mixtures by laser-heating targets placed on optical fiber tips using a 1064 nm laser. (PDF, 903 KB, 2006)

Subsidence data gathered by the U.S. Bureau of Mines over a series of longwall panels in the Pittsburgh Coalbed were studied to obtain insight as to the role of time in the subsidence process. These results were then compared to data from three other sites in the northern Appalachian Coal Basin to determine if the true characteristics of the subsidence process had been observed. (PDF, 645 KB, 1995)

The Bureau of Mines has successfully used sulfur hexafluoride (SF6) as a tracer gas to measure mine air flows under conditions where conventional methods have failed. SF6 was employed experimentally to measure accurately recirculation of return into intake air caused by leakage through an old stoped area, to check for potential leakage from an adjacent mine, to trace 10,000 cfm of "lost" air from an intake airway, and to measure transit air time through uranium mines. It proved useful as a means of accurately measuring airflow volumes in airways of large cross section and very low flow velocity and in determining the recirculation resulting from underground cooling plants. (PDF, 781 KB, 1974)

The Bureau of Mines performed laboratory experiments to evaluate the triboelectric effect of particulate-laden gas streams on polyethylene pipe at various velocity, humidity, dust-size, and dust-load conditions. (PDF, 1104 KB, 1986)

This report reviews experimental evidence indicating a relative permeability effect that causes the flow of methane to increase with time when a coalbed is degassed by boreholes. (PDF, 607 KB, 1975)

The Bureau of Mines is developing underground gob gas drainage as an alternate means of methane control for U.S. longwalls. Holes are drilled into the roof over the panel and on retreating longwalls, towards the working face from a location inby the face. Although this cross-measure method of degasification has been used successfully in Europe, some of these techniques cannot be directly applied to U.S. mines. This is the first study of its kind in this country. (PDF, 1143 KB, 1982)

Methane-drainage holes must be completely filled by grout before mining to prevent the emission of large quantities of gas during mine-through, which would constitute an explosion hazard. In November 1980, seven horizontal holes at the multipurpose borehole, a small-diameter shaft drilled as a Bureau of Mines coalbed methane-drainage installation on the property of the Federal No. 2 Mine, Monongalia County, West Virginia, were plugged using a sodium silicate gel grout. This report describes the grout mix and the use of the grout at the multipurpose borehole, and discusses the results observed upon mine-through of the holes in early 1981. Cost data for the sodium silicate grout are also presented. (PDF, 2863 KB, 1984)

A study where the response times of machine-mounted methane monitors were measured by placing the methane sensor heads in a specially designed box where they were exposed to an atmosphere containing a constant concentration of methane (PDF, 240 KB, 2004)

Over the years, more than 20,000 mine seals have been erected in underground coal mines in the United States. The National Institute for Occupational Safety and Health is conducting research to develop design guidelines, to investigate noninvasive techniques to characterize seal strength properties, and to evaluate seal test methods. (PDF, 8648 KB, 2002-02)

This paper describes research conducted to compare the performance, including response time and accuracy, of selected instruments using infrared and catalytic sensors. (PDF, 393 KB, 2008)

Coalbeds exhibit a directional permeability, with the maximum permeability oriented parallel to the face cleat. Thus, the most efficient pattern of vertical degasification holes for a coalbed is dependent upon cleat orientation. Analysis of surface joints was the only technique considered sufficiently reliable on a local basis. Prediction of cleat orientation is based on the pairing of the principal directional sets into all reasonable combinations of fundamental systems. The system or systems composed of the most dominant sets nearest to 90 deg. Separation are likely to be a reliable prediction of cleat orientation. The most dominant set of the system selected is likely to be the face cleat. (PDF, 705 KB, 1976)

To reduce the weight and bulk of equipment that mining personnel must carry underground, the Bureau of Mines and the Mining Enforcement and Safety Administration (MESA) investigated accurate and convenient gas samplers for use by mine inspectors in sampling mine atmospheres. The samplers are septum- stoppered glass vials commonly used for routine blood sampling. These lightweight, compact samplers yeild results comparable with those obtained with conventional bottle samplers of 250-ml nominal capacity. (PDF, 395 KB, 1975)

An experimental degasification program using a vertical borehole and vacuum pump to drain gas from the gob area of a longwall panel was successful at Bethlehem Mines Corporation, Cambria Division, No. 33 coal mine. Sixty-one million cubic feet of methane has been exhausted during a 9-month period. Daily production time in the panel increased as a result of lower methane levels in the returns. (PDF, 797 KB, 1969)

This paper describes NIOSH research demonstrating that the ventilation of large-opening mines improves significantly by including ventilation requirements in the mine planning process and implementing some practical techniques during mining. (PDF, 529 KB, 2008)

The Bureau of Mines found sulfur hexafluoride (SF6), released from a lecture bottle, to be an ideal gaseous tracer for studying mine ventilation systems. In a Pennsylvania limestone mine, this technique was useful in evaluating the effectiveness of auxiliary fans, measuring low flow velocities, probing the air circulating near a working face region where ventilation appeared to be poor, and estimating volumetric flow rates in airways of large cross-sectional area and having low flow velocities. This technique was also used in a western vein-type metal mine to measure the amount of return air being recirculated into the intake air due to leakage through old stoped areas. (PDF, 1017 KB, 1974)

The fact that methane ignitions continue to occur at the mining face indicates that monitoring with machine-mounted methanometers does not always indicate the presence of high methane concentrations. Methane concentrations at the face change quickly due to changes in airflow. By measuring these changes in airflow, it may be possible to predict changes in face methane levels more quickly. The effects of changes in airflow direction and turbulence on instrument readings are discussed, and guidelines are given for selecting the type of instruments to be used for monitoring airflow near the mining face. (PDF, 390 KB, 2007)

A test system was developed at NIOSH's ventilation test gallery to measure airflow using a three-axis ultrasonic anemometer. The gallery was used to simulate face airflow conditions in underground mines having a blowing curtain. Airflow data were used to draw airflow profiles for different curtain setback distances, intake flow quantities, and entry widths. In addition, methane was released at the face, measured at the sampling locations, and displayed as methane distributions in the areas between the curtain and the face. (PDF, 1764 KB, 2006-01)

Describes a test system developed for measuring airflow in the NIOSH ventilation gallery using a three-axis ultrasonic anemometer. (PDF, 760 KB, 2005)

Describes a NIOSH study of how much ventilation air reaches the end of a 40 foot box cut. Tests were run to determine how much ventilation air reaches the end of the box cut with the continuous miner at three locations in the 40-ft two-pass extended cut mining sequence; at the end of the 40-ft box cut, at the start of the 40-ft slab cut, and 6.1 m (20 ft) into the slab cut. (PDF, 468 KB, 1999-07)

Describes three alternative ventilation models for use in large opening underground mines with respect to their use in mines of various levels of development. (PDF, 3260 KB, 2004-02)

In Europe, water infusion is used widely to reduce generation of respirable dust during mining. Its use in the United States is limited to a few plow operations in the Pocahontas No. 3 Coalbed. This Bureau of Mines report describes the technology for infusing water into a longwall panel and reports the results of a recent demonstration in the Lower Sunnyside Coalbed that achieved dust reductions averaging 58 pct. (PDF, 832 KB, 1983)

This Bureau of Mines report deals with water infusion of coalbeds, which can control methane emission at face areas during developmental mining and which may sometimes suppress dust. Studies show that water infused into the coalbed flows through the fracture system and displaces the methane in the fractures and prevents migration from the solid coal. Displaced gas migrates away from the face area that has been water infused and enters the return ventilation airways. Respirable dust levels were reduced by about 75 pct on a longwall section in the Pocahontas No. 3 Coalbed and by about 50 pct on a development section in the upper Kittanning coalbed, but no statistically reliable reduction was found in the respirable dust levels in the Pittsburgh coalbed. (PDF, 1980 KB, 1977)

This report analyzed MSHA accident statistics for 2002 to explore the relationship between the age of injured workers and their job titles, severity of the accident, the types of accident they had, total mining experience, and experience at the mine where they were working when the accident occurred. (PDF, 590 KB, 2006)