Abstract
The Occupational Safety and Health Administration (OSHA) has proposed amending its existing exposure regulations for methylene chloride. The National Institute for Occupational Safety and Health (NIOSH) tested organic vapor cartridges and canisters for their breakthrough characteristics against methylene chloride. These tests were conducted to determine breakthrough times for methylene chloride with commercially available, negative-pressure organic vapor cartridge and canister respirators. Various methylene chloride challenge concentrations, from a low of 50 ppm to a high of 1000 ppm, were employed. Cartridges and canisters were tested “as received” from the manufacturer at a flow rate of 64 L/min through the respirator; 50 percent and 80 percent relative humidities were used. Breakthrough times (tb) were determined for individual cartridges and canisters, as well as for stacked cartridges. The results indicate that cartridge breakthrough times (tb) were extremely short when tested at 80 percent relative humidity (RH) for all the challenge concentrations. The chinstyle canisters, which contained 2.5–3.0 times more sorbent than the cartridges, gave a tb of only 100 minutes when tested at 125 ppm and 80 percent RH. The frontmounted/back-mounted canisters (10.5–11 times more sorbent than cartridges) gave a tb of more than 10 hours at 125 ppm and 80 percent RH, but the tb was reduced to only 5 hours when the challenge concentration was increased to 1000 ppm.