CFI Fire Dynamics & Behavior Flashcards

What is the stoichiometric ratio in fire chemistry?

Answer: The ideal fuel-to-air mixture ratio for complete combustion

The stoichiometric ratio is the theoretically perfect fuel-to-air mixture that allows complete combustion with neither excess fuel nor excess oxygen.

Which fire behavior phenomenon describes the movement of flames along the underside of a ceiling or overhead accumulation of hot gases before flashover?

Answer: Rollover

Rollover (also called flameover) occurs when unburned gases that have collected at the ceiling level ignite and flames roll along the ceiling surface.

The 'lower flammable limit' (LFL) of a gas refers to:

Answer: The minimum concentration of gas in air that can sustain combustion

The LFL is the minimum concentration (percentage by volume in air) of a flammable gas below which the mixture is too lean to ignite or propagate flame.

In NFPA 921, what does the term 'fire pattern' specifically refer to?

Answer: Visible or measurable physical changes or identifiable shapes caused by a fire effect

Per NFPA 921, a fire pattern is a visible or measurable physical change or an identifiable shape caused by a fire effect such as char, smoke deposition, or heat damage.

What is pyrolysis in the context of fire investigation?

Answer: The chemical decomposition of a material by heat without combustion

Pyrolysis is the thermal decomposition of a solid or liquid material into simpler chemical compounds through the application of heat without direct combustion.

Which factor most significantly affects the angle of a fire's V-pattern on a wall surface?

Answer: The rate of heat release and intensity of the fire

Higher heat release rates produce wider, shallower V-patterns, while slow, low-intensity fires produce narrower, more pointed V-patterns on wall surfaces.