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Methylene Chloride Facts No. 9
Suggested Work Practices for
Cold Degreasing and Other Cold Cleaning Operations
Occupational Safety and Health Administration (1998)
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On January 10, 1997, the Occupational Safety and Health Administration (OSHA) issued a
standard that lowered the limit on worker exposures to methylene chloride (MC). This new
standard greatly reduces the chance of developing health problems from working in
facilities that use MC.
Worker exposures to MC occur mainly through breathing its vapors. MC can also pass
through workers' skin if it gets on their body or clothes. Occasionally, workers can
swallow small amounts of MC if they don't wash their face and hands before eating, or if
they eat in contaminated work areas. Short-term exposure to high levels of MC can cause
dizziness, headaches, a lack of coordination, and irritation of the skin, eyes, mucous
membranes, and respiratory system. Long-term exposure causes cancer in laboratory animals.
Studies in workers suggest an association between MC exposures and certain types of
cancer. OSHA considers MC to be a potential occupational carcinogen. Exposure to MC may
also make the symptoms of heart disease (e.g., chest pains, angina) worse.
About 23,717 facilities that perform cold degreasing and cold cleaning operations use
MC. During cold cleaning, a rag covered with solvent (MC) is used to manually clean dirty
parts. During cold degreasing, dirty parts are sprayed with MC, soaked in a degreasing
tank, and drained. In many facilities, just improving work practices and housekeeping
procedures can greatly reduce exposure to MC. The following suggested practices may help
you reduce your workplace exposures.
Keep MC Vapors Contained
- Store and transport MC only in approved safety containers.
- Properly label all MC containers to indicate their contents, hazards, and proper use,
storage, and disposal. Read these labels and follow the directions.
- Keep MC containers closed tightly when not in use.
- Avoid unnecessary transfer or movement of cleaning solutions.
- Keep degreasing tanks covered when not in use.
- Place rags used for cold cleaning in a closed container (preferably a non-aluminum,
all-metal safety container) immediately after use.
- When spraying parts, keep the nozzle as low as possible in the tank. This will help keep
MC vapors in the degreaser and out of the work area.
Avoid Breathing MC Vapors
- Turn on the degreasing tank ventilation system at least an hour before work begins or
leave it on overnight.
- Avoid breathing air directly above the degreasing tank. Do not lean over the tank when
working. Use long-handled tools for scrubbing
- Only stand near the degreasing tank when you have to load, unload, or manually clean
parts (even if the degreaser is covered).
- Carefully remove parts after degreasing to prevent them from swinging back and forth
(rocking). Rocking increases drag out of MC vapors which is a major source of MC exposure.
- Do not work or stand between the degreasing tank or MC-covered parts and the exhaust
system.
- Avoid breathing the air directly above rags and parts during cold cleaning.
- Do not rely on the odor of MC to warn you of over- exposure. People cannot smell MC
until vapor concentrations are above 300 ppm, which is 12 times higher than the 8-hour
time-weighted average permissible exposure limit of 25 ppm. Also, your sense of smell can
quickly get used to the odor of MC so that you stop noticing it.
- If you become dizzy, light-headed, or have other symptoms of MC exposure, go immediately
to an area with fresh air.
Avoid Direct Skin Contact with MC
- Wear two pairs of gloves when using MC. The inner glove should be made of polyethylene
(PE)/ethylene vinyl alcohol (EVOH), PE, or laminate to prevent MC penetration. The outer
glove should be made of nitrile or neoprene to protect against puncture or rips. [Note:
Because MC can readily penetrate nitrile and neoprene, wearing just the outer glove will
not protect your skin from MC exposure.]
- Wear shoulder length gloves, or the longest gloves possible.
- Before use, inspect gloves for pin-holes, cracks, thin spots, softening, swelling, and
stiff or sticky surfaces.
- Change gloves frequently, before breakthrough occurs.
- Rotate several pairs of gloves throughout the day.
- Let gloves dry in a warm, well-ventilated area at least overnight before reuse.
- Wear rubber aprons and boots or shoe covers to prevent MC from getting on your clothes
which results in prolonged skin contact with MC.
- Wear a face shield or goggles to protect your face and eyes.
- Use the washing facilities in your work area to wash off any MC from your hands and
face.
- Use lots of soap or mild detergent and water to clean grease, oil, dirt, or anything
else off your skin. Do not use MC or other organic solvents to clean your skin.
Minimize the Chance of Spills and Leaks
- Develop and follow procedures for containing MC spills or leaks.
- Frequently inspect the degreasing tank and MC containers for cracks, loose parts, and
other possible sources of leaks.
- Clean up all spills and leaks as quickly as possible.
- Place rags, waste, paper towels, or absorbent used to clean spills in a closed container
(preferably a non-aluminum, all-metal safety container) immediately after use.
- Make sure that leaks are repaired and spills cleaned up by employees who are trained in
proper cleanup methods. These employees should wear appropriate personal protective
equipment (PPE).
Take Extra Precautions in Low and Confined Spaces
MC vapors are heavier than air so they tend to move to low, unventilated spaces such as
tanks and maintenance pits. Degreasing tanks must be cleaned regularly.
- Do not enter or lean into the degreasing tank or any other low-lying confined area until
it has been completely aired out and tested. Wear proper PPE and follow the appropriate
confined space entry procedures outlined in OSHA's Permit Required Confined Spaces standard
(29 CFR 1910.146).
- Use a supplied-air respirator when cleaning the degreasing tank.
- Use a long-handled tool to pick up items that you drop into a confined space or
low-lying area.
Take Personal Precautions
- After working with MC, always wash your face and hands before eating.
- Never eat in the work area or your food and drink could become contaminated with MC.
- Avoid drinking alcohol before or after being exposed to MC. Alcohol can lower the amount
of MC needed to cause health problems.
- Be alert when working with MC. Avoid situations that might result in overexposure.
- If your clothes become soaked with MC, remove them and take a shower. Do not put your
clothes back on until they are thoroughly clean and dry.
Respirators
If engineering controls and work practices do not reduce MC exposures to an acceptable
level, workers must wear supplied-air respirators. Respirators are the least preferred
method of controlling employee exposures. Supplied-air respirators must have a clean air
supply through the use of compressed air tanks containing air meeting at least the
requirements for Grade D breathing air, or a breathing air type compressor with the air
intake located in an area with a clean air supply.
CAUTION: Filter cartridge respirators cannot be used because MC can
pass through available cartridges leaving respirator wearers unprotected.
Compliance Schedule
Employers with less than 20 employees have until:
- February 4, 1998 to implement paragraph (d) (Initial Monitoring).
- April 10, 2000 to implement paragraph (f) (Engineering Controls).
- April 10, 1998 to implement all other provisions.
Employers with more than 20 employees have until:
- September 7, 1997 to implement paragraph (d) (Initial Monitoring).
- April 10, 1998 to implement paragraph (f) (Engineering Controls).
- December 21, 1997 to implement all other provisions.
Additional Resources
For more information concerning consultation assistance, contact the
nearest OSHA office (look under state listings for the Department of Labor),
refer to the listings on
OSHA's web site,
or contact OSHA's Office of Information at (202) 219-8151.
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