NFST NFST Fire Behavior and Science 2 — Questions and Answers
Question 1: Which extinguishing agent is most effective on a Class A fire involving ordinary combustibles like wood and paper?
- Dry chemical
- CO2
- Water (Correct answer)
- Halon
Correct answer: Water
Water is the primary and most effective agent for Class A fires because it cools burning material below ignition temperature.
Question 2: What term describes the lowest temperature at which a liquid fuel produces enough vapor to ignite?
- Boiling point
- Flash point (Correct answer)
- Auto-ignition temperature
- Combustion threshold
Correct answer: Flash point
Flash point is the minimum temperature at which a liquid gives off enough vapor to form an ignitable mixture near its surface.
Question 3: Smoke rising quickly and freely from a building generally indicates what about the fire conditions inside?
- The fire is fully developed
- There is adequate ventilation and the fire is oxygen-rich (Correct answer)
- A backdraft is imminent
- The fire has self-extinguished
Correct answer: There is adequate ventilation and the fire is oxygen-rich
Smoke that rises quickly and freely indicates the fire has a good oxygen supply and is burning in a well-ventilated space.
Question 4: What is the primary purpose of ventilation during a structure fire?
- To increase oxygen supply for firefighters
- To remove heat, smoke, and gases to improve visibility and reduce fire spread (Correct answer)
- To cool the building structure
- To create a backdraft to extinguish the fire
Correct answer: To remove heat, smoke, and gases to improve visibility and reduce fire spread
Ventilation removes heat, smoke, and toxic gases from a structure, improving conditions for search and rescue and suppression efforts.
Question 5: Which phase of fire development is characterized by limited fuel and plentiful oxygen?
- Fully developed phase
- Decay phase
- Incipient (growth) phase (Correct answer)
- Flashover
Correct answer: Incipient (growth) phase
During the incipient or growth phase, the fire is small, fuel is abundant but consumption is low, and oxygen is plentiful.
Question 6: What phenomenon occurs when burning liquid fuel floats on water and spreads, potentially worsening a flammable liquid fire?
- Slop-over
- Boilover (Correct answer)
- Froth-over
- Surge-over
Correct answer: Boilover
Boilover occurs when water beneath a burning oil layer turns to steam, causing a violent eruption that spreads burning fuel.
NFST NFST Fire Behavior and Science 2
Which extinguishing agent is most effective on a Class A fire involving ordinary combustibles like wood and paper?