F01 Fire Classification & Extinguishers 2 — Questions and Answers

Question 1: Which class of fire involves flammable liquids such as gasoline, oil, or paint thinner?

Class A
Class B (Correct answer)
Class C
Class D

Correct answer: Class B

Class B fires involve flammable and combustible liquids, including gasoline, oil, grease, tar, oil-based paint, lacquer, and flammable gases.

Class B fires are fueled by flammable liquids and gases. For F-01 fireguards overseeing torch operations, Class B hazards are especially relevant because propane and other fuel gases used in torches fall into this category. Class B extinguishers (CO2, dry chemical, or foam) should be immediately available at any hot work site.

Question 2: A CO2 (carbon dioxide) fire extinguisher is most effective on which types of fires?

Class A (ordinary combustibles) only
Class D (combustible metals) only
Class B and C fires (liquids and electrical) (Correct answer)
Class K (cooking oils) only

Correct answer: Class B and C fires (liquids and electrical)

CO2 extinguishers work by displacing oxygen and are rated for Class B (flammable liquids) and Class C (electrical) fires without leaving residue.

Carbon dioxide extinguishers discharge CO2 gas, which displaces the oxygen that fires need to sustain combustion. They are rated B and C because they do not leave a conductive residue (making them safe on live electrical equipment) and are effective on liquid/gas fires. They have limited effectiveness on deep-seated Class A fires, as CO2 dissipates quickly and embers can re-ignite.

Question 3: What does the letter 'A' rating on a fire extinguisher indicate?

The extinguisher is approved for aircraft use
The extinguisher capacity in gallons
The extinguisher is effective on ordinary combustibles (Correct answer)
The extinguisher is approved for asphalt work

Correct answer: The extinguisher is effective on ordinary combustibles

The 'A' classification on a fire extinguisher means it is rated for Class A fires involving ordinary combustibles such as wood, paper, cloth, and plastics.

NFPA and FDNY recognize Class A as fires in ordinary solid combustibles — wood, paper, textiles, plastics, and similar materials. Extinguishers with an 'A' rating use water, foam, or multi-purpose dry chemical agents that cool the burning material and interrupt combustion. On a hot work site, Class A extinguishers guard against sparks igniting nearby wood or debris.

Question 4: Which extinguisher type should NEVER be used on electrical fires?

Carbon dioxide (CO2)
Dry chemical (ABC)
Water (stored pressure) (Correct answer)
Halotron

Correct answer: Water (stored pressure)

Water is electrically conductive and must never be used on live electrical equipment. It can cause electrocution and spread the fire.

Water-based extinguishers (including water mist and stored-pressure water) are rated only for Class A fires. Applying water to a Class C (electrical) fire risks electric shock to the operator because water conducts electricity back through the stream to the user. FDNY hot work sites often have electrical equipment nearby; fireguards must ensure only properly rated extinguishers (CO2, dry chemical rated C) are available.

Question 5: How should a fireguard hold a portable fire extinguisher when using the PASS technique?

Aim at the top of the flames and sweep side to side
Aim at the base of the fire and use a side-to-side sweeping motion (Correct answer)
Hold the nozzle still and aim at the center of the fire
Aim at the ceiling above the fire to disperse agent downward

Correct answer: Aim at the base of the fire and use a side-to-side sweeping motion

PASS stands for Pull, Aim, Squeeze, Sweep. The nozzle should be aimed at the BASE of the fire and swept side to side to knock down and extinguish flames at their fuel source.

The PASS technique is the standard method for operating a portable extinguisher: Pull the pin, Aim the nozzle at the base of the fire, Squeeze the handle, and Sweep side to side. Aiming at the base cuts the fire off from its fuel. Aiming at flames above the fuel merely burns the agent without effect. F-01 fireguards must be proficient in PASS to respond immediately to ignitions during torch operations.

Question 6: What minimum fire extinguisher rating is typically required at a hot work site under FDNY regulations?

1-A:10-B:C
2-A:20-B:C (Correct answer)
4-A:40-B:C
10-A:80-B:C

Correct answer: 2-A:20-B:C

FDNY and NFPA 51B require at least a 2-A:20-B:C rated extinguisher within 30 feet of hot work operations to handle typical fire scenarios.

NFPA 51B (Standard for Fire Prevention During Welding, Cutting, and Other Hot Work) specifies that a minimum 2-A:20-B:C extinguisher must be at the hot work location. FDNY enforces this requirement for F-01 certified fireguards. The higher B rating accounts for flammable gases and liquids associated with torch operations, while the C rating addresses electrical hazards present at construction sites.

F01 Fire Classification & Extinguishers 2

Which class of fire involves flammable liquids such as gasoline, oil, or paint thinner?