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Toxic Yield.


pdf icon Toxic Yield. (219 K)
Pitts, W. M.

Technical Basis for Performance Based Fire Regulations. A Discussion of Capabilities, Needs and Benefits of Fire Safety Engineering. United Engineering Foundation Conference. Proceedings. United Engineering Foundation, Inc. January 7-11, 2001, San Diego, CA, United Engineering Foundation, Inc., New York, NY, Cox, G., Editor(s), 76-87 pp, 2001.

Keywords:

regulations; fire safety; safety engineering; toxic products; experiments; carbon monoxide; fire chemistry; fire fatalities; fire gases; fire hazard; room fires; underventillated combustion

Abstract:

It is generally recognized that the vast majority of deaths associated with accidental enclosure fires are due to smoke inhalation. Older reviews of autopsy results suggested that the fraction was on the order of 2/3. In the United States there is evidence that this number has been growing in recent years and is approaching 3/4. Autopsy results have also shown that the vast majority of these fire victims have carboxyhemoglobin levels in their bloodstreams sufficient to induce incapacitation or death. This has led many researchers to conclude that carbon monoxide (CO) is the dominant toxicant present in fire gases. It is recognized that the elevated carbon dioxide (CO2) levels (which result in increased respiration rates) and depressed oxygen (O2) levels associated with the fire gases act together to increase the susceptibility of victims to CO asphyxiation. The importance of CO toxicity is highlighted by the conclusion that most victims in the United States are overcome at locations remote from the room of fire origin. In recognition of the central role that CO plays in smoke inhalation fire deaths and the fact that mechanisms for CO formation in fires were poorly understood, the National Institute of Standards and Technology initiated an investigation of CO formation in fires over a decade ago. In the interim, significant progress has been made on identifying the formation mechanisms for CO within an enclosure containing a fire. As will be discussed, additional investigation is necessary to provide an adequate understanding of the subsequent reaction and transport of CO upon exiting the fire enclosure. This paper focuses on the current understanding of CO formation mechanisms in real-scale fires with a particular emphasis on post-flashover generation.