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VOL. 13 NO. 11
Take a class

Fire extinguishers 101

What type is best for your boat?

Fire extinguishers 101

Fire extinguishers come in three classes, A, B and C, which match the type of fire they extinguish:

  • Class A fire: wood, paper, rubber, plastic, textiles
  • Class B fire: flammable liquids (gasoline, oil and grease)
  • Class C fire: electrical equipment

A fire extinguisher will carry a label showing the class of fire for which it’s best suited.

The most widely available, least expensive and most practical fire extinguisher for a recreational boat is a dry chemical type that’s made to put out two classes of fires: B and C. Plain water, which is almost always available, will extinguish a Class A fire.

Dry chemical extinguishers, which are the most popular and reasonably priced, are generally Type BC extinguishers. They leave a messy residue that will cause corrosion unless cleaned up immediately.

Fixed extinguisher systems are available for use in engine compartments and enclosed spaces. These extinguishers are designed for automatic deployment and can be invaluable in saving a boat with an engine fire. Their use is strongly recommended for any boat with an inboard, inboard/outboard, or jet drive engine in an enclosed space. They will discharge without opening the engine compartment, thus avoiding the risk of adding oxygen. Do not enter a compartment after a fixed system has discharged until the compartment has cooled and been well ventilated to avoid reigniting a fire by introducing air into the compartment.

Portable extinguishers should never be mounted in the engine compartment.

Sizes of fire extinguishers

Dry chemical extinguishers come in two sizes to describe the amount of extinguishing chemical it holds per U.S. Coast Guard regulations:

  • Size I dry chemical extinguishers must contain a minimum of 2 pounds of dry chemical.
  • Size II extinguishers require at least 10 pounds of dry chemical.

Fire extinguisher requirements

Fire extinguishers are required on boats with

  • inboard engines and outboard boats with closed compartments for storing permanent or portable tanks,
  • permanently installed fuel tanks, and
  • closed compartments or living spaces.

Type B, gasoline or fuel fires, are the most common type experienced on a boat, so that’s the type specified in the requirements.

Purchase only extinguishers certified as Coast Guard-approved by an independent testing agency such as Underwriters Laboratories Inc. Look for the part of the label that reads “Marine Type USCG.”

The minimum number of portable extinguishers required depends on the length of the boat.

Fire extinguisher locations

Mount your extinguishers away from the fire hazards so that you will be able to get to them safely. Make sure they don’t project into a busy passageway. Steering stations, galleys and passenger cockpits are logical locations. If you sleep aboard, keep one near your bunk.


  • Check your extinguisher gauges monthly to make sure they’re at full pressure. Gauges may occasionally be unreliable. Be sure the discharge nozzle is clean; insects love to build nests inside.
  • Slowly rock your dry chemical extinguishers from an upright to an upside-down position several times. If you feel a thud, the chemical is stuck together and the extinguisher will no longer function properly.
  • Immediately replace and properly dispose of old extinguishers. Size I and Size II can be recharged. Check for corrosion or mechanical damage to the extinguisher case. If they are the rechargeable type (metal head, not plastic), take them to a qualified fire extinguisher service for an annual inspection.

How to use a fire extinguisher

The key to controlling a fire is to put it out while it’s still small. Your chances are better if you have more than the minimum required extinguishers. Hold the extinguisher upright and use the P.A.S.S. (pull, aim, squeeze, sweep) technique:

  • Pull the safety pin, usually located around the handle of the extinguisher.
  • Aim the fire extinguisher at the base of the fire.
  • Squeeze the handle and begin to discharge the extinguisher.
  • Sweep the extinguisher side to side while aiming at the base of the fire until the fire is out.

Many local fire departments provide practice opportunities.

Never partially discharge extinguishers to test them; they may leak and become unusable. Always recharge or replace partially discharged extinguishers. Purchase only Coast Guard-approved extinguishers designed for marine use.

To learn more, take our America’s Boating Course.

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