CFPS Fire Dynamics and Behavior 2 — Questions and Answers
Question 1: What term describes the minimum temperature at which a liquid fuel produces enough vapor to ignite when an ignition source is present?
- Fire point
- Flash point (Correct answer)
- Autoignition temperature
- Boiling point
Correct answer: Flash point
Flash point is the minimum temperature at which a liquid produces sufficient vapor to momentarily ignite in the presence of an ignition source.
Question 2: During flashover, the approximate temperature in the upper gas layer typically reaches:
- 200–300°F (93–149°C)
- 400–500°F (204–260°C)
- 900–1200°F (482–649°C) (Correct answer)
- 1800–2000°F (982–1093°C)
Correct answer: 900–1200°F (482–649°C)
Flashover occurs when the upper gas layer reaches approximately 900–1200°F (482–649°C), causing all combustible surfaces in the compartment to simultaneously ignite.
Question 3: Which combustion product is the leading cause of fire fatalities in the United States?
- Carbon dioxide
- Hydrogen cyanide
- Carbon monoxide (Correct answer)
- Acrolein
Correct answer: Carbon monoxide
Carbon monoxide is the leading cause of fire-related fatalities because it is colorless, odorless, and rapidly incapacitates victims at relatively low concentrations.
Question 4: The flammable (explosive) range of a gas is bounded by the:
- Flash point and fire point
- Lower Flammable Limit (LFL) and Upper Flammable Limit (UFL) (Correct answer)
- Autoignition temperature and piloted ignition temperature
- Stoichiometric ratio and excess air coefficient
Correct answer: Lower Flammable Limit (LFL) and Upper Flammable Limit (UFL)
The flammable range is defined by the LFL (minimum fuel-air mixture that sustains combustion) and UFL (maximum mixture that sustains combustion).
Question 5: A fuel package that is burning at the maximum rate limited by available oxygen rather than fuel surface area is said to be:
- Fuel-controlled
- Ventilation-controlled (Correct answer)
- Thermally thin
- Stoichiometrically balanced
Correct answer: Ventilation-controlled
A ventilation-controlled fire cannot increase its heat release rate because oxygen supply is the limiting factor, not the available fuel.
Question 6: The 'two-layer model' of compartment fire behavior refers to:
- Solid fuel pyrolysis and vapor-phase combustion zones
- A hot upper gas layer and a cooler lower layer separated by a thermal interface (Correct answer)
- Flame and smoldering combustion occurring simultaneously
- Radiative and convective heat transfer acting on separate surfaces
Correct answer: A hot upper gas layer and a cooler lower layer separated by a thermal interface
The two-layer model describes the hot, buoyant smoke layer accumulating at the ceiling and the cooler, cleaner air layer remaining near the floor.
Question 7: Backdraft is most likely to occur when a fire compartment has been:
- Fuel-controlled throughout its entire development
- Ventilation-controlled and then suddenly receives fresh air (Correct answer)
- Extinguished with water and allowed to cool for 30 minutes
- Over-ventilated and all available fuel has been consumed
Correct answer: Ventilation-controlled and then suddenly receives fresh air
Backdraft occurs when a ventilation-controlled, oxygen-depleted compartment receives a sudden inflow of fresh air, causing rapid ignition of accumulated unburned gases.
CFPS Fire Dynamics and Behavior 2
What term describes the minimum temperature at which a liquid fuel produces enough vapor to ignite when an ignition source is present?