Carbon Monoxide and Water Vapour Contamination of Compressed Breathing Air for
Firefighters and SCUBA Divers

Austin CC, Ecobichon DJ, Dussault G, Tirado C

Abstract

Compressed breathing air, used in self-contained breathing apparatus by firefighters and other categories of workers as well as by recreational and commercial divers, is prepared with the aid of high pressure compressors operating in the range of 5000 psig. There have been reports of unexplained deaths of SCUBA divers and anecdotal accounts of decreased time to exhaustion in firefighters using SCBA's. Compressed breathing air has been found to contain elevated levels of carbon monoxide (CO) and water vapour which are consistent with carboxyhemoglobin (COHb) poisoning and freezing of the user's regulator on the breathing apparatus. The Coburn-Forster-Kane equation (CFK equation) was used to estimate COHb levels at rest and at maximum exercise when exposed to different levels of CO in contaminated breathing air. The results demonstrated that, at maximum exercise, the COHb ranged from 6.0 to 17 percent with the use of one to four SCBA cylinders contaminated by 250 ppm of CO. Standard operating procedures have been developed for a large Municipal Fire Department to minimize the risk of compressed breathing air contamination. Results of the quality analysis/quality control program indicate that implementation of these procedures has improved the quality of the compressed breathing air. Recommendations are made for improvement of the air testing procedures mandated by the Canadian CAN3 180.1-M85 Standard on Compressed Breathing Air and Systems.

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