National Toxicology Program

SUBSTANCE IDENTIFICATION

Cellulose insulation (CI) is a type of thermal insulation consisting of recycled newspapers treated with fire retardant chemicals. There is no information on fiber size of the cellulosic material in the final product.

Technical Products and Impurities: CI may contain fire retardant chemicals, most often boric acid, borax or ammonium sulfate; buffers such as gypsum; residuals of the paper production process (e.g., sodium hydroxide, sodium sulfide, formaldehyde, chlorine, fluorine, lead, iron, sulfur compounds); and remnants of dyes, resins, gums, talc, printing inks, and various solvents (Davis, 1993; Lea, 1995).

Performance Standards

In 1978, the Consumer Product Safety Commission (CPSC) issued performance standards to ensure the safety of CI. These standards required that all CI produced after September 7, 1978, must pass flammability and corrosiveness tests specified in General Services Administration (GSA) standard HH-I-515-C that mandates performance of CI products purchased by government agencies. Under the CPSC standards, CI must have a flame spread rating of from 0 to 25 when placed in a 25-foot Steiner tunnel and ignited. In addition, the insulation must pass a corrosiveness test since some chemical treatments used to reduce cellulose flammability can corrode metal and undermine a building's structural integrity (Anon., 1978a). These standards were amended in October, 1979 to reflect the newer version of the federal standard HH-I-515-D, to tighten flammability and corrosion standards and mandate updated labeling. The amended standard requires a critical radiant flux test on samples, instead of tests in a Steiner tunnel; replaces the blown-density test methods employed with cyclone shaker tests; requires more exacting procedures for determining the corrosiveness of the samples; and requires that labels state that the product meets the amended law. The amendment also requires all flammability test specimens to have a critical radiant flux greater than or equal to 0.12 watt/cm² and bans the use of any CI tested that causes perforations in copper, aluminum, or steel coupons in a 14-day corrosion test. (Anon., 1979a). The CPSC standard, although it does not encompass as many tests as the GSA standard, is mandatory for all manufacturers (Chrenka, 1980).

There are two standard specifications issued by the American Society for Testing and Materials (ASTM) pertaining to CI. ASTM C 739-91 covers the composition and physical requirements of chemically treated, recycled cellulosic fiber (wood-base) loose-fill type thermal insulation for use in attics or enclosed spaces in housing and other framed buildings within the ambient temperature range from -45.6 to 82.2°C (-50 to 180°F) by pneumatic or pouring application. ASTM C 1149-90 covers the physical properties of self-supported spray applied cellulosic fibers intended for use as thermal or acoustical insulation, or both, and covers chemically treated cellulosic materials intended for pneumatic applications where temperatures do not exceed 82.2°C (180°F) and where temperatures will routinely remain below 65.6°C (150°F). Both standards address density, thermal resistance, smoldering combustion, fungal resistance, corrosion, moisture vapor absorption, and odor. In addition, ASTM C 739-91 for loose-fill thermal insulation addresses average critical radiant flux and starch content, and ASTM C 1149-90 for spray-applied cellulosic insulation addresses surface burning characteristics, adhesive/cohesive strength, flame resistance permanency, substrate deflection, and air erosion (ASTM, 1994a,b).