Fire Safety Fire Behavior and Combustion Science 2 — Questions and Answers
Question 1: What is a backdraft?
- A fire that spreads backward due to prevailing wind direction
- The reverse flow of smoke out of a building through vents
- An explosive ignition caused when fresh oxygen is suddenly introduced to a superheated, oxygen-depleted fire (Correct answer)
- A fire that originates in the basement and travels upward
Correct answer: An explosive ignition caused when fresh oxygen is suddenly introduced to a superheated, oxygen-depleted fire
Backdraft occurs when a smoldering, oxygen-deficient fire is suddenly supplied with fresh air — often by opening a door — triggering a rapid, explosive ignition.
Question 2: Which mechanism of heat transfer carries heat upward through the movement of hot gases and air?
- Conduction
- Radiation
- Convection (Correct answer)
- Combustion
Correct answer: Convection
Convection transfers heat through the physical movement of heated gases and air; hot gases rise due to buoyancy, spreading heat and fire to upper levels.
Question 3: What is the flashpoint of a flammable liquid?
- The temperature at which the liquid begins to boil
- The lowest temperature at which its vapors will ignite momentarily when exposed to an ignition source (Correct answer)
- The temperature at which the liquid will self-ignite without a spark
- The temperature at which the liquid produces the maximum heat output
Correct answer: The lowest temperature at which its vapors will ignite momentarily when exposed to an ignition source
Flashpoint is the lowest temperature at which a flammable liquid produces sufficient vapor to ignite briefly when exposed to an external ignition source.
Question 4: Which warning signs most strongly indicate a potential backdraft condition inside a structure?
- Flames visible through windows and rapidly rising smoke
- Smoke being drawn inward, discolored (yellow/brown) windows, and little visible flame (Correct answer)
- Sprinklers activating and fire alarms sounding throughout the building
- Rapid fire spread across the ceiling with thick black smoke
Correct answer: Smoke being drawn inward, discolored (yellow/brown) windows, and little visible flame
Backdraft conditions are indicated by smoke being pulled back inside, stained windows from pyrolysis gases, and minimal visible flame — signs of a hot, oxygen-starved fire.
Question 5: Heat transfer through direct physical contact between materials is called:
- Convection
- Radiation
- Conduction (Correct answer)
- Combustion
Correct answer: Conduction
Conduction transfers heat through direct contact between materials, such as a metal structural beam conducting heat from a fire to an adjacent uninvolved room.
Question 6: What is 'rollover' (also called flameover) in fire development?
- Flashover occurring across multiple rooms simultaneously
- Flames rolling across the ceiling layer as unburned gases ignite before full flashover (Correct answer)
- Fire spreading by rolling along the floor
- The rotation of a fire caused by ventilation currents
Correct answer: Flames rolling across the ceiling layer as unburned gases ignite before full flashover
Rollover occurs when unburned gases accumulating at the ceiling reach their ignition temperature and ignite, creating flames rolling across the ceiling — a warning sign that flashover is imminent.
Question 7: Which factor most significantly controls the intensity and spread rate of a fire?
- The color of interior wall surfaces
- The age and construction year of the building
- The availability of oxygen (Correct answer)
- The outdoor humidity level
Correct answer: The availability of oxygen
Oxygen availability is the primary factor controlling combustion intensity; more oxygen allows faster, hotter burning while reduced oxygen slows or stops combustion.
