Chemical cartridge respirator performance: 1,3-butadiene

The chemical 1,3-Butadiene recently has been classified as a potential occupational carcinogen; subsequently, a reduction in the 8 hr TWA from 1000 ppm to 10 ppm has been proposed. Substantial quantities of 1,3-Butadiene are produced annually for use in the manufacture of a variety of rubber compounds, foams, resins and chemicals. Existing process environments may present a potential health hazard under the proposed standards, and the need for proper respiratory protection is evident. As a result, the performance of Scott organic vapor (642-OV), organic vapor/acid gas (642-OA) and acid gas (642-AG) twin cartridges has been determined for 1,3 butadiene. A cartridge test system was developed to generate challenge concentrations of 100 ppm and 1000 ppm; an infrared analyzer was used to measure breakthrough at 10 ppm. The residence time modeling concept developed previously was used to produce the performance characteristics for three types of activated carbon for residence times of 0.1 less than or equal to tau less than or equal to 1.0 sec. Kinetic adsorption capacities and adsorption rate constants were computed from this data, and cartridge performance also was predicted. The twin cartridges tested demonstrated reasonable adsorption capacity for 1,3 butadiene. Cartridge service life was found to be inversely proportional to airflow rate; it was reduced at elevated temperature and humidity conditions. Breakthrough times were approximately three times longer at 100 ppm than at 1000 ppm. When clean air was drawn through cartridges saturated with 1000 ppm 1,3 butadiene, desorption occurred readily. The rate of desorption and the peak concentration were found to be dependent upon the temperature, humidity and degree of saturation.