Fires can be classified into four groups:
Class A-Fires in ordinary combustible materials such as mattresses, dunnage, wood, canvas, etc. These fires are best extinguished by the cooling effects of water or water fog.
Class B-Fires in such as gasoline, oil, lubricating oil, diesel oil, tar, greases, etc. The blanketing or smothering effect of the extinguishing agent is important.
Class C-Fires in live electrical equipment, such as switchboard insulation, transformer terminals, etc. The extinguishing agents must be nonconducting so that electrical shock is not experienced by the firefighter.
Class D-Fires in combustible metals like magnesium, sodium, titanium, lithium, etc.
Except for a fire caused by a catastrophic event, a fire starts out small.
If it is discovered, it can probably be extinguished by one of the portable extinguishers.
Different types of fires require different types of extinguishers. Portable extinguishers are placed aboard ship according to the type of hazard that might be seen in the space where they are located. Portable extinguishers are first aid measures only and are not intended as a substitute for hose lines when the fire is beyond the limitations of the extinguisher in use. Here are the types of fires for which each portable extinguisher can be used:
1. Water (stored pressure type). Use on class A fires. Do not use on electrical fires.
How to operate: Break the seal and pull the locking pin. Direct the nozzle at the base of the fire. Grip the lever and squeeze.
Maintenance: Inspect monthly for full pressure and physical condition. Discharge and refill with fresh water annually.
2. Foam (stored pressure type). Use on class Aand class B fires. Do not use on electrical fires.
How to operate: Break the seal and pull the locking pin. Direct the nozzle at the base of the fire. Grip the lever and squeeze.
Maintenance: Inspect monthly for full pressure and physical condition. Annually discharge and refill with fresh foam solution or replace the foam hose cartridge (depending on design).
3. Carbon dioxide. Use on class B and class C fires. C02 extinguishers are not permitted in passenger and crew quarters.
How to operate: Break the seal and pull the locking pin. Hold the nozzle on the insulated handle, squeeze the lever, and direct the gas at the base ofthe fire.
Maintenance: Inspect monthly for condition of seal and bottle. Weigh the bottle annually. If the net weight without the hose and horn is down by 10 percent of the full charge then the bottle requires recharging. Re-hydro the bottle every 12 years if the bottle did not require recharging during that interval.
4. Halon 1211. Use on class B and class C fires. Some of the larger capacity Halon bottles may have an A rating. Check the face of the bottle for specifics.
How to operate: Break the seal and pull the locking pin. Direct the nozzle at the base of the fire. Grip the lever and squeeze.
Maintenance: Inspect monthly for full pressure gauge reading and physical condition. Check the pressure gauge and weigh the bottle annually. Rehydro at intervals required by the D.O.T. Interval will depend on the standards to which the bottle was built. Both Halon 1211 and 1301 may be used in portable extinguishers.
5. Dry chemical. The class of fire for which the extinguisher is effective will depend on the dry chemical in it. Check the face of the bottle for specifics.
Sodium bicarbonate and potassium bicarbonate: Use on class B and class C fires.
Mono-ammonium phosphate: Use on class A, class B, and class C fires. How to operate: Depends on the design of the extinguisher.
External cartridge dry chemical type: Pull the hose up sharply to break the seal. Press the activation plunger. Squeeze the lever on the discharge hose to confirm the powder flow before committing to the fire. Discharge the powder at the base of the fire.
Stored pressure type: Break the seal and pull the locking pin. Direct the hose at the base ofthe fire and squeeze the lever.
Maintenance: Inspect monthly for full pressure gauge on stored pressure extinguisher. Inspect all types for condition of hose and container.
6. Dry powder. The term dry powder has been reserved exclusively by the National Fire Protection Association (NFPA) to describe powdered agents which are intended for use on class D fires. The extinguishing agent must be matched to the class D material of concern. There is no powder that is effective against all of the 26 class D metals. Fire extinguishers are now provided with symbols that are displayed on the bottle to show which type of fire the extinguisher is effective against: A, B, C, or D.
1. Soda acid. Use on class A fires. Do not use on electrical fires.
How to operate: Turn upside down. Direct nozzle at base offire. Recharge. Maintenance: Inspect monthly for condition. Annually discharge and refill.
2. Foam. Use on class A and class B fires. Do not use on electrical fires.
How to operate: Turn upside down. Direct nozzle at base of fire. Recharge. Maintenance: Inspect monthly for condition. Discharge and refill annually.
