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NOTE: This is an unformatted excerpt from our online fire protection training library.

Fire Behavior- Introduction to Fire Suppression

Fire Chemistry

Ignition

Before one can understand how a fire is mitigated, one must first understand some of the basic concepts of ignitionIgnition is defined as the process by which self-sustained combustion is started..

When a flammable vaporA vapor is defined as the gaseous state of a material that is liquid or solid under ordinary conditions is ignited, a small spark will result in a flame that can spread throughout an entire area. A liquid must emit enough but not too muchThe liquid's "flammable limits" define the ability of the material to be ignited in the presence of air. If there is not enough vapor in the mixture, then the mixture is too "lean," and combustion can't take place. If there is too much vapor in the mixture, then the mixture is too "rich," and ignition can't occur., vapor into the air in order to create the proper air/vapor mixture for ignition to take place.

An energy source that heats a solid fuel must be strong enough to break down a material's chemical structure into its basic chemical elements in order to create a vapor emission reaction. In the classic example of a stuffed couch, the materials of construction may include foam rubberFoam rubber is a petrochemical-based substance, which means that the materials of construction started out as some level of crude oil, and have been refined and reacted. Once enough heat is generated, the foam rubber breaks down, returning to its original elements or some variation of them. The result can be akin to developing gasoline-type substances, emitting vapors very similar to gasoline vapors. . The fire ignites the vapors given off from the couch cushions as the materials of construction break down in the presence of the heat sourceThe classic example of this is the person that falls asleep on the couch smoking a cigarette. If conditions are right, the heat of the cigarette will cause the vaporization of a small part of the cushion, and this vaporization may take place for long periods before there is a "combustible" moisture near the area where the cigarette first fell. .

Click here to view a video of a couch fire set as part of a training exercise.

NOTE: This is an unformatted excerpt from our online fire protection training library.

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