FE Extinguishing Agent Properties & Chemistry 1 — Questions and Answers
Question 1: What is the primary extinguishing mechanism of ABC dry chemical agents such as monoammonium phosphate?
- Cooling the fuel surface below ignition temperature
- Interrupting the chemical chain reaction of combustion (Correct answer)
- Diluting oxygen concentration below 15%
- Forming a physical barrier over the fuel
Correct answer: Interrupting the chemical chain reaction of combustion
ABC dry chemical agents interrupt the free-radical chain reaction in the flame, which is the primary mechanism by which they extinguish fires.
Question 2: Which extinguishing agent is electrically non-conductive and leaves virtually no residue after discharge?
- Dry chemical (monoammonium phosphate)
- Carbon dioxide (CO2) (Correct answer)
- AFFF foam
- Wet chemical potassium acetate
Correct answer: Carbon dioxide (CO2)
Carbon dioxide (CO2) is electrically non-conductive and dissipates completely as a gas, leaving no residue on equipment or surfaces.
Question 3: Purple-K dry chemical extinguishing agent contains which primary chemical compound?
- Monoammonium phosphate
- Sodium bicarbonate
- Potassium bicarbonate (Correct answer)
- Potassium chloride
Correct answer: Potassium bicarbonate
Purple-K is a potassium bicarbonate-based dry chemical agent, which is approximately twice as effective as sodium bicarbonate on Class B fires.
Question 4: Carbon dioxide (CO2) extinguishes fires primarily by which two mechanisms?
- Chemical chain interruption and fuel removal
- Oxygen displacement and cooling (Correct answer)
- Saponification and smothering
- Emulsification and dilution
Correct answer: Oxygen displacement and cooling
CO2 extinguishes fire by displacing oxygen (smothering) and by absorbing heat energy, providing a cooling effect on the burning material.
Question 5: Halon 1211 (bromochlorodifluoromethane) is classified as what type of extinguishing agent?
- Wet chemical agent
- Inert gas agent
- Halogenated agent (Correct answer)
- Dry powder agent
Correct answer: Halogenated agent
Halon 1211 is a halogenated (halocarbon) agent that extinguishes fire by chemically interrupting the combustion chain reaction.
Question 6: What is the approximate specific gravity of carbon dioxide gas compared to air at standard conditions?
- 0.7 (lighter than air)
- 1.0 (same weight as air)
- 1.5 (heavier than air) (Correct answer)
- 2.5 (much heavier than air)
Correct answer: 1.5 (heavier than air)
CO2 has a specific gravity of approximately 1.5 relative to air, which causes it to settle at low points and displace oxygen effectively in enclosed spaces.
Question 7: Sodium bicarbonate dry chemical is rated for use on which fire classes?
- Class A and B fires only
- Class B and C fires only (Correct answer)
- Class A, B, and C fires
- Class D fires only
Correct answer: Class B and C fires only
Sodium bicarbonate (ordinary dry chemical) is rated for Class B (flammable liquids) and Class C (energized electrical) fires but is not effective on Class A fires.
FE Extinguishing Agent Properties & Chemistry 1
What is the primary extinguishing mechanism of ABC dry chemical agents such as monoammonium phosphate?