![]() During this initial phase of fire development, radiant heat warms adjacent fuel and continues the process of pyrolysis. Air in the compartment provides adequate oxygen to continue fire development. Once combustion begins, development of an incipient fire is largely dependent on the characteristics and configuration of the fuel involved (fuel controlled fire). Going back to the basics of fire behavior, ignition requires heat, fuel, and oxygen. (Click Figure 3 for a larger view of the concept map.) are important, but need to be integrated into the B-SAHF framework to provide a more complete picture.įigure 3 integrates the concept maps presented in previous articles and outlines some of the major interrelationships between the B-SHAF fire behavior indicators. Flame indicators such as location, volume, color, etc. ![]() However, do not get so focused on visible flames that you miss more important, but subtle building, smoke, air track, and heat indicators. It is important to remember that our personal protective equipment provides significant insulation and slows the transfer of heat and resulting sensation of changes in temperature.įlame: Flaming combustion is often the most obvious or visible indicator observed by firefighters. Heat: While heat cannot be observed directly, observation of the effect of heat on air track (i.e., velocity of smoke discharge), the building or exposures, and sensation of changes in temperature can be significant fire behavior indicators. It is critical that firefighters begin their assessment of smoke and air track indicators from outside the building, but continue this process on an ongoing basis from both the interior and exterior of the structure. The location and appearance of smoke can provide valuable cues related to the location of the fire, its burning regime (fuel or ventilation controlled) and the stage of fire in various areas of the building. Smoke and Air Track: Smoke conditions and the pattern of smoke and air movement are two of the most important indicators of fire behavior. This pre-fire assessment of likely fire development and spread should be compared with actual fire behavior encountered during emergency incidents to improve skills in reading building factors. While many common types of buildings and occupancies (such as single family dwellings) are not the focus of a formal preplan program, firefighters can examine common features and their influence on fire behavior. smoke conditions and flames).īuilding: Unlike the other fire behavior factors, the building and its contents are present prior to ignition and can be examined during the preplanning process. building construction) and others are quite dynamic, changing as the fire develops (i.e. Some factors are relatively unchanging (i.e. However, fire behavior indicators encompass a wide range of factors that firefighters may see, hear, or feel. (see Figures 1 and 2.)įirefighters can easily observe some of the B-SAHF indicators. Flashover is not a stage of development, but simply a rapid transition between the growth and fully developed stages. Recognizing the stages of fire development and likely progression through this process allows firefighters to predict what will happen next (if action is not taken), potential changes due to unplanned ventilation (such as failure of a window), and the likely effect of tactical action.Ĭompartment fire development can be described as being comprised of four stages: incipient, growth, fully developed and decay (see Figure 1). ![]() Remember that fire conditions can vary considerably throughout the building with one compartment containing a fully developed fire, an adjacent compartment in the growth stage, and still other compartments yet uninvolved. Part of the process of reading the fire involves recognizing the stages of fire development that are involved. This is the first of two articles focused on fire behavior indicators and the stages of fire development. Understanding the indicators is important, but more important is the ability to integrate these factors in the process of reading the fire as part of size-up and dynamic risk assessment. Previous articles have addressed building factors, smoke, air track, heat, and flame (B-SAHF) as critical fire behavior indicators.
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