Boating Basics Online - Basic Boating Safety Course
Chapter 4 - Required Equipment

Fire Extinguishers

Next in line after PFDs, fire extinguishers are a very important safety item. Although not all motorboats are required to carry a fire extinguisher, it is highly recommended that you do. There are numerous types and sizes of extinguishers but each one has to be U. S. Coast Guard approved.

Fire Extinguishers are classified by letters and numbers according to the class and size fire they can put out. The letter, (A, B, C, or D) indicates the class of fire. The number is a measure of the capacity of the extinguisher - the larger the number, the greater the capacity of extinguishing material to put out a fire.

Type A Fire
"A" is for combustible solids like wood.

Type B Fire
"B" is for flammable liquids such as gasoline.

Type C Fire
"C" is for electrical fires.

Type D Fire
"D" is for combustible metals like magnesium

Some boat fires involve burning wood and paper (Class A), but these fires can be put out with water. Do not use water on gasoline, oil, or electrical fires. Water causes gasoline and oil fires to spread and electrical current is conducted through the water.

Make sure to inspect your fire extinguishers monthly to make sure they are properly stored, charged and undamaged.

Once you use a fire extinguisher, you should either have it recharged, if it is rechargeable, or replaced if it is a disposable type. In any event, always make sure that your extinguisher label indicates that it is a U.S. Coast Guard approved marine type device.

Fire Extinguisher Charge Indicator

Which extinguisher is best for which type of fire?

Type of Extinguisher Class of Fire Notes:

Carbon Dioxide

B, C Carbon Dioxide is a class B, C, agent only. Because of the CO2 high pressure, it is not recommended for use on Class A, ember and ash-based fires because of the hazard of spreading the fire when blasting it with the high pressure gas.
Dry Chemical B, C Dry chemical extinguishers come in three varieties. Sodium Bicarbonate B, C (Alkaline); Potassium Bicarbonate, Purple "K", B, C (Alkaline); and Mono Ammonium Phosphate A, B, C (Acidic). The A, B, C dry chemical is not recommended for marine use for two reasons:
  • It is corrosive
  • The way in which this agent obtains its class A rating is its ability to melt, seep and encase. This necessitates dismantling of equipment to repair or rebuild.
Foam A, B Foam extinguishers are water based and quench Class A fires. They also blanket, smother and separate the vapor layer in Class B fires.

Make sure your fire extinguisher(s) is/are located where readily accessible.

Fire Precaution

Remove one element and you have no fire.

An onboard fire is a serious event. If the fire cannot be controlled, where do you go except in the water? The fire triangle consists of fuel, oxygen and heat. All three must be present to start a fire, and the removal of any single one can extinguish a fire.

Fuels, such as gasoline and propane, can be very dangerous if precautions are not taken. The fumes of these fuels are heavier than air and tend to collect in the cabin, bilge and other lower areas of the boat. It is essential that you keep these areas clean and free of trash because they naturally are surrounded by oxygen all that is necessary to start a fire is heat. This could come from something as simple as a spark from an ignition component. All you did was turn the key to start the engine and boom.

You should read and understand the instructions on your fire extinguisher(s). If a fire starts, you should be prepared and not hesitate. Grab the fire extinguisher, activate it, and direct it at the base of the flames using short bursts and sweeping it from side to side. (More on this in the Chapter on Accidents.)

If underway and a fire starts, stop the boat and position it in such a manner that the fire is downwind. Order everyone to put on lifejackets. If possible, try to turn off the fuel source to the fire. Grab the extinguishers and control the fire.


Pull Pin

Aim at base of flame

Squeeze handle

Sweep side to side


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