Carbon monoxide contamination of compressed breathing air for firefighters and divers:

Austin CC, Ecobichon DJ, Dussault G, Tirado C.Department of Occupational Health, Faculty of Medicine, McGill University, Montreal, Quebec, Canada.

Compressed breathing air, used in self-contained breathing apparatus (SCBA) 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 SCBAs. Compressed breathing air has been found to contain elevated levels of carbon monoxide (CO) and water vapor that 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% with the use of 1 to 4 SCBA cylinders contaminated by 250 ppm CO. Standard operating procedures have been developed at the Montreal 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.

When carbon monoxide is present in the air you breathe, the CO combines with hemoglobin in your blood, preventing the hemoglobin from doing its job of supplying oxygen to your bodies cells and tissues. As aresult, some cells and tissues do not receive enough oxygen and they die. Exposure to a low concentration of CO over a short time causes headaches, disorientation, andgrogginess. Constant low-level exposure produces neurological disorders and symptoms similar to those ofParkinson's Disease. A higher concentration of CO can result in heart attack or may have permanentconsequences; damage to the neurological system and brain, memory loss, and impaired coordination.Coma and death almost always result from exposure to a high concentration (above 30%) of carbonmonoxide.