FE Fire Extinguisher Types & Classification 3 — Questions and Answers
Question 1: A Class D extinguisher agent must be matched to the specific metal fuel because:
- All metal fires burn at the same temperature
- Different combustible metals require different compatible agents to avoid violent reactions (Correct answer)
- Class D agents are universally effective on all metals
- Metal fires are always extinguished with water
Correct answer: Different combustible metals require different compatible agents to avoid violent reactions
Using an incompatible Class D agent on a specific metal can cause violent reactions, so agent selection must match the metal involved.
Question 2: The 'B' numerical rating on a Class B extinguisher (e.g., 10-B) represents:
- The agent weight in pounds
- The approximate square footage of flammable liquid fire it can extinguish (Correct answer)
- The discharge time in seconds
- The operating pressure in PSI
Correct answer: The approximate square footage of flammable liquid fire it can extinguish
The numerical B rating approximates the square footage of a flammable liquid fire in a one-foot-deep pan that the unit can extinguish.
Question 3: Which extinguisher agent works by forming a vapor-suppressing aqueous film over flammable liquid surfaces?
- Purple-K (PKP)
- Aqueous Film-Forming Foam (AFFF) (Correct answer)
- Sodium bicarbonate dry chemical
- Carbon dioxide
Correct answer: Aqueous Film-Forming Foam (AFFF)
AFFF creates an aqueous film that spreads across flammable liquid surfaces, cutting off oxygen and suppressing vapors.
Question 4: When an extinguisher carries a Class C rating only (no A or B), what does this mean operationally?
- It can extinguish any type of fire near electrical equipment
- The agent is non-conductive but the unit has not been rated for fuel or combustible fires (Correct answer)
- It is specifically designed for energized electrical panels only
- It contains halon as its agent
Correct answer: The agent is non-conductive but the unit has not been rated for fuel or combustible fires
A stand-alone Class C rating means the agent won't conduct electricity, but the unit lacks sufficient agent to earn A or B ratings.
Question 5: Multipurpose dry chemical (ABC) extinguishers use which primary agent?
- Sodium bicarbonate
- Potassium bicarbonate
- Monoammonium phosphate (Correct answer)
- Potassium chloride
Correct answer: Monoammonium phosphate
Monoammonium phosphate is the agent in multipurpose ABC dry chemical extinguishers because it is effective on Class A, B, and C fires.
Question 6: A cooking appliance fire involving burning vegetable oil in a deep fryer is classified as:
- Class A
- Class B
- Class F
- Class K (Correct answer)
Correct answer: Class K
In the US, fires involving cooking oils and fats in commercial cooking equipment are classified as Class K.
Question 7: Which of the following extinguisher types operates without any stored propellant pressure, relying instead on a chemical reaction to generate gas upon activation?
- Stored-pressure water extinguisher
- Cartridge-operated dry chemical extinguisher
- Pump-tank water extinguisher (Correct answer)
- CO2 extinguisher
Correct answer: Pump-tank water extinguisher
Pump-tank extinguishers have no stored pressure; the user manually pumps to generate discharge pressure at the time of use.
FE Fire Extinguisher Types & Classification 3
A Class D extinguisher agent must be matched to the specific metal fuel because: