Classes of Fire
The pictograms on the left may be found on the newer extinguishers and the pictograms on the right may be found on some of the older extinguishers. In either case it identifies the class of fire the fire extinguisher may be used to extinguish a fire.
| Type of Fire | Symbol | Description |
|---|---|---|
| Class A |  |
Fires involving ordinary combustibles like wood, paper, many plastics, cloth, and rubber. At proper distance (maximum range of discharge stream) pull the safety pin and squeeze lever. Aim extinguisher at the base of the fire toward the front edge and sweep side to side, move closer as fire gets smaller. Sixty-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, and gases. Dry chemical extinguishers require operation similar to water extinguishers, but technique is 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 that involve energized electrical equipment. 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 re-ignition after fire appears out. Always recharge. Does not leave moisture or corrosive residue. |
| Class D |  |
Fires that involve combustible metals. (e.g., magnesium, titanium, sodium, lithium, and potassium) |