Fire Progression Phenomena

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Rapid Fire Progression Phenomena
Brian J. Rocker Jr.
American Military Institute

Fire fighters are killed every year due to lack of knowledge on the job. This paper focuses on numerous studies that have been conducted on the lack of knowledge regarding enclosure fire behavior, to include: backdraft, flameover, and flashover. This paper, based off the National Fire Protection Association, (NFPA), attempts to combine the many definitions and “truths” floating around about these such phenomena, and clearly define them, and explain the process and possible indicators of these very likely events within an enclosure. With studies performed by scientists, such as (Dunn) and (Quintiere), this paper explains the lack of knowledge and training those within the fire service profession have today. Keywords: backdraft; flameover; flashover

Rapid Fire Progression Phenomena
Many firefighters are killed in the line of duty everyday due to rapid fire progression phenomena. Statistics show that enclosure fires are the most dangerous to the fire community. A 2001 study proved that four out of every five fire deaths occurred in residential structure fires. (Cote 10-11) This study confirmed the fear that many in the fire profession do not understand thoroughly about the deadly killers: backdraft, flashover, and flameover. This paper discusses the need for achieving a higher knowledge of fire behavior, especially enclosure fire behavior. The purpose of this study is to make everyone aware about the current lack of training and education regarding these rapid fire progression phenomena. This paper not only provides a basis for each phenomena, making them easier to understand, but to provide solutions for helping fire safety personnel understand all the components involved in a rapid evolving enclosure fire.

Backdraft has not been studied as much as the other rapid fire phenomena. A few studies however have been performed to aid in better understanding of the nature behind it. A team from the University of California, Fleischmann and Pagni were among the first to explore the science of backdraft through experimentation. (Fleischmann, 1993) They created a small-scale compartment and were able to reproduce the phenomena, and have been one of the only successful studies for almost a decade. They discovered that “If the compartment is closed, the excess pyrolyzates accumulate, ready to burn when a vent is suddenly opened, for example, as may happen when a window breaks due to the fire-induced thermal stress or a firefighter enters the compartment. Upon ventilation, gravity current will carry fresh air into the compartment. This air mixes with the excess pyrolyzates to produce a flammable, premised gas, which can be ignited in many ways.” (Fleischmann, 1993) However a better definition by NFPA standards states “A deflagration resulting from the sudden introduction of air into a confined space containing oxygen-deficient products of incomplete combustion.” (International Fire Service Training Association, 2001) In better terms, limited ventilation within an enclosure fire can produce large amounts of unburnt pyrolysis products. When a rapid gust of oxygen enters the enclosure, it mixes with the unburned pyrolysis products creating combustible gases. When ignited from an ignition source, a rapid burning begins by shooting out of the entrance from which it originated from, causing a fireball out of the enclosure. A few indicators include a pulsing structure with smoke seeping in and out under pressure, no visible flames in the room, hot doors and windows, whistling sounds around doors, and discolored or cracked window glass. (Quintiere, 1998)

Flashover has been the subject of a numerous of studies beginning way back in the 1960s by the British scientist Phillip H. Thomas. (Grimwood, 2003) His initial understanding and definition of flashover was inaccurate, however it was the first time thought was given to this fire...
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