CPS Fire Behavior and Combustion 1 — Questions and Answers
Question 1: What are the three elements of the fire triangle?
- Fuel, oxygen, and heat (Correct answer)
- Fuel, carbon dioxide, and pressure
- Oxygen, water, and heat
- Fuel, nitrogen, and ignition
Correct answer: Fuel, oxygen, and heat
The fire triangle consists of fuel, oxygen, and heat — all three must be present simultaneously for combustion to occur.
Question 2: Which phase of combustion produces the visible flames seen during a structural fire?
- Incipient phase
- Free-burning phase (Correct answer)
- Smoldering phase
- Flashover phase
Correct answer: Free-burning phase
The free-burning phase is characterized by visible, active flames and rapid consumption of available fuel and oxygen.
Question 3: What is flashover in a structure fire?
- The moment a backdraft explosion occurs
- The near-simultaneous ignition of all exposed combustible surfaces in a compartment (Correct answer)
- When fire spreads through an HVAC system
- The point at which sprinklers activate
Correct answer: The near-simultaneous ignition of all exposed combustible surfaces in a compartment
Flashover occurs when radiant heat raises all combustible surfaces in a compartment to their ignition temperature, causing near-simultaneous ignition.
Question 4: Which type of heat transfer occurs when heat moves through a material by direct molecular contact?
- Convection
- Radiation
- Conduction (Correct answer)
- Pyrolysis
Correct answer: Conduction
Conduction is heat transfer through direct molecular contact within or between materials, such as heat traveling through a metal door handle.
Question 5: At approximately what oxygen concentration (by volume) will most fires self-extinguish?
- 18%
- 15% (Correct answer)
- 21%
- 10%
Correct answer: 15%
Most fires cannot sustain combustion when oxygen concentration drops to approximately 15% or below, making oxygen removal an effective suppression strategy.
Question 6: Which fire class involves fires in ordinary combustible materials such as wood, paper, and cloth?
- Class B
- Class C
- Class A (Correct answer)
- Class D
Correct answer: Class A
Class A fires involve ordinary combustibles like wood, paper, cloth, rubber, and many plastics, which are the most common fire type encountered.
Question 7: What is backdraft?
- A fire that burns downward through flooring
- An explosion caused by the sudden introduction of oxygen into an oxygen-depleted, superheated environment (Correct answer)
- Flame spread driven by wind currents
- Smoke traveling back through an exhaust duct
Correct answer: An explosion caused by the sudden introduction of oxygen into an oxygen-depleted, superheated environment
Backdraft occurs when fresh oxygen enters a hot, oxygen-starved compartment, causing rapid ignition of accumulated unburned gases and a powerful explosion.
CPS Fire Behavior and Combustion 1
What are the three elements of the fire triangle?