CFI CFI Fire Dynamics & Behavior 1 — Questions and Answers
Question 1: What term describes the minimum temperature at which a liquid fuel produces enough vapor to ignite momentarily when an ignition source is applied?
- Flash point (Correct answer)
- Fire point
- Auto-ignition temperature
- Piloted ignition temperature
Correct answer: Flash point
The flash point is the lowest temperature at which a liquid produces sufficient vapor to form an ignitable mixture near its surface.
Question 2: Which heat transfer mechanism involves the movement of hot combustion gases rising from a fire and spreading heat throughout a compartment?
- Conduction
- Radiation
- Convection (Correct answer)
- Advection
Correct answer: Convection
Convection transfers heat through the physical movement of hot gas molecules, causing them to rise and circulate within a compartment.
Question 3: The transition from a localized fire to full room involvement where all combustible surfaces ignite simultaneously is called:
- Backdraft
- Flashover (Correct answer)
- Rollover
- Smoke explosion
Correct answer: Flashover
Flashover occurs when radiant heat from the hot gas layer raises all exposed combustible surfaces to their ignition temperature simultaneously.
Question 4: What condition occurs when fresh air suddenly enters a vitiated (oxygen-depleted) compartment containing hot unburned gases, causing a rapid deflagration?
- Flashover
- Rollover
- Backdraft (Correct answer)
- Boilover
Correct answer: Backdraft
Backdraft is a smoke explosion caused by the sudden introduction of oxygen into a superheated, oxygen-depleted compartment full of unburned fuel gases.
Question 5: Which of the following best describes the 'heat release rate' (HRR) in fire dynamics?
- The temperature at which fuel ignites
- The rate at which a fire produces thermal energy measured in kilowatts (Correct answer)
- The speed at which flames travel across a surface
- The amount of oxygen consumed per unit of fuel
Correct answer: The rate at which a fire produces thermal energy measured in kilowatts
Heat release rate (HRR), measured in kilowatts or megawatts, is the single most important variable in fire dynamics as it determines fire growth and severity.
Question 6: In fire investigation, 'char depth' measurements are primarily used to:
- Determine the exact ignition temperature of wood
- Estimate relative burn time and intensity to help identify fire origin (Correct answer)
- Measure the moisture content of structural lumber
- Calculate the total fuel load in a compartment
Correct answer: Estimate relative burn time and intensity to help identify fire origin
Char depth provides investigators with comparative data about relative burn duration and heat intensity at various locations, aiding in origin determination.
CFI CFI Fire Dynamics & Behavior 1
What term describes the minimum temperature at which a liquid fuel produces enough vapor to ignite momentarily when an ignition source is applied?