Fire Safety Fire Extinguisher Types and Usage 5 — Questions and Answers
Question 1: A CO2 extinguisher is used in a small enclosed room. What safety concern must users be aware of?
- CO2 displaces oxygen and can cause asphyxiation (Correct answer)
- CO2 produces toxic fumes when it contacts flames
- CO2 becomes flammable at high concentrations
- CO2 reacts with metal surfaces and causes corrosion
Correct answer: CO2 displaces oxygen and can cause asphyxiation
CO2 extinguishers displace oxygen in confined spaces, creating a risk of asphyxiation for anyone remaining in the area.
Question 2: What distinguishes a stored-pressure extinguisher from a cartridge-operated extinguisher?
- Stored-pressure uses the same chamber for agent and propellant; cartridge-operated keeps them separate (Correct answer)
- Cartridge-operated extinguishers are always larger than stored-pressure types
- Stored-pressure extinguishers can only be used once
- Cartridge-operated extinguishers do not require recharging
Correct answer: Stored-pressure uses the same chamber for agent and propellant; cartridge-operated keeps them separate
In stored-pressure units, propellant and agent share one chamber, while cartridge-operated units store propellant in a separate cartridge that punctures upon activation.
Question 3: Which class of fire extinguisher is marked with a green triangle?
- Class A (Correct answer)
- Class B
- Class C
- Class D
Correct answer: Class A
Class A extinguishers are identified by a green triangle symbol, indicating suitability for ordinary combustibles like wood, paper, and cloth.
Question 4: When using the PASS technique, what does the second 'S' stand for?
- Sweep (Correct answer)
- Spray
- Scan
- Stop
Correct answer: Sweep
In the PASS acronym (Pull, Aim, Squeeze, Sweep), the second S stands for Sweep — moving the nozzle side to side at the base of the fire.
Question 5: An extinguisher rated for Class D fires is needed when dealing with which type of burning material?
- Combustible metals such as magnesium, titanium, or sodium (Correct answer)
- Diesel fuel and other petroleum distillates
- Electrical panels and motor control centers
- Dense wooden structures and timber
Correct answer: Combustible metals such as magnesium, titanium, or sodium
Class D extinguishers are specifically formulated for fires involving combustible metals, which require dry powder agents incompatible with water or standard dry chemicals.
Question 6: What annual maintenance action is required for all portable fire extinguishers per NFPA 10?
- A thorough inspection by a trained person (Correct answer)
- A full hydrostatic pressure test
- Complete discharge and recharge of the agent
- Replacement of all seals and tamper indicators
Correct answer: A thorough inspection by a trained person
NFPA 10 requires an annual maintenance inspection by a qualified person to verify all mechanical parts, agent, and expellant are in operable condition.
Question 7: Why should you never use a standard dry chemical extinguisher on a Class D metal fire?
- It can react violently with burning metals and intensify the fire (Correct answer)
- It lacks sufficient pressure to reach combustible metal fires
- It coats the metal in a layer that traps heat inside
- It only works at temperatures below those of metal fires
Correct answer: It can react violently with burning metals and intensify the fire
Standard dry chemical agents can react exothermically with burning metals like sodium or potassium, causing violent reactions that worsen the fire.
Fire Safety Fire Extinguisher Types and Usage 5
A CO2 extinguisher is used in a small enclosed room.
What safety concern must users be aware of?