Evaluation of OSHA method 5 for measuring chloroform in pulp and paper industry workplace and ambient atmospheres

As a result of the recent lowering of the Occupational Safety and Health Administration's (OSHA's) permissible exposure limit (PEL) for chloroform from 50 ppm to 2 ppm, interest has increased in measuring chloroform in pulp and paper industry workplace atmospheres. OSHA suggested that its Method 5 should be used for measuring chloroform concentrations in the range of the new PEL. There are some potential problems with using Method 5 for this purpose. Pulp and paper industry atmospheres may interfere with the measurement because of high temperature, high humidity, and the presence of chlorine. The charcoal sorbent tubes specified in OSHA Method 5 were challenged in the laboratory with a test gas containing 0.1, 0.5, 1, and 2 times the PEL of chloroform at 38 degrees C with 80% to 93% relative humidity and ca. 0.5 ppm chlorine. Application of the National Institute for Occupational Safety and Health (NIOSH) validation protocol to the results indicated a bias of -8.2% and a pooled coefficient of variation (CV) of 0.0274. The method CV is less than the critical CV; thus, the method is acceptable by the NIOSH validation protocol under these conditions. Field testing of OSHA Method 5 was successful and did not reveal any unexpected problems. Additional tests showed that with some modification, OSHA Method 5 can be used to measure chloroform concentrations in ambient atmospheres down to 0.1 ppb.