Fire Extinguishers
Class A Fires
Involve ordinary combustibles like wood, paper, many plastics, cloth, rubber- Pressurized water extinguisher
- At proper distance (maximum range of discharge stream), pull safety pin and squeeze lever. Aiming at base of fire at front edge and sweeping side to side, move closer as fire gets smaller.
- 60 second discharge duration; may be used intermittently; maximum range 30-40 feet.
- Works by cooling.
- Always recharge.
Class B fires
Involve flammable liquids, oils, greases, gases- Dry chemical extinguishers: either multipurpose A:B:C or combination B:C
- Dry chemical extinguishers require operation similar to water extinguishers, but technique more critical because of shorter (12-20 foot) range.
- Duration of discharge 8-25 seconds.
- Work by blanketing fuel and interrupting chemical chain reaction at fuel surface.
- Continue blanketing to prevent reignition after fire appears to be out.
- Always recharge.
Class C fires
Involve energized electrical equipment- Combination B:C carbon dioxide (CO2)) extinguishers
- Commonly used on Class C fires; identifiable by horn.
- Nonconductive extinguishing agent required because of electrical shock hazard.
- Operation similar to above, but short (3-8 foot) range and short (8-30 seconds) discharge time.
- Works by displacing oxygen, smothering fire.
- Continue discharging to prevent reignition after fire appears out.
- Always recharge.
- Does not leave moisture or corrosive residue.
A:B:C or B:C Halon extinguisher
- Operation is similar to CO2, but has a longer range (up to 15-20 feet) and short (8-15 seconds) discharge time.
- Works by interrupting the chemical chain reaction at fuel surface.
- Continue discharging to prevent reignition after fire appears to be out.
- Always recharge.
- Does not leave moisture or corrosive residue.