Fire Extinguishers

Chris Riley by Chris Riley Updated on June 28, 2020. In nauticalknowhow

Chapter IV – Legal Requirements

Section 2c – 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.

boating safety course A
“A” is for combustible solids like wood.

boating safety course B
“B” is for flammable liquids such as gasoline.

boating safety course C
“C” is for electrical fires.

boating safety course D
“D” is for combustible metals like magnesium

Although some boat fires involve burning wood and paper (Class A), 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. Portable extinguishers should be mounted where they are readily accessible. Check the gauge to make sure the extinguisher is still charged. Check the seals to make sure they have not been tampered with. Replace cracked or broken hoses and keep nozzles free from obstruction. You should also weigh them to assure that they meet the minimum weight stated on the label.

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.

boating safety course fire extinguishers

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, amber and ash based fires. Why? Because of the hazard of spreading the fire when blasting it with the high pressure gas.
(until year 2000)
A, B, C Halon 1211 carries the A, B, C rating only in a capacity of 9 pounds. Units smaller than 9 pounds only carry the B, C rating. Halon gas vaporizes to quickly to maintain a Class A fire in small quantities.
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 it 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.

All power boats, except outboards, less than 26 feet and of open construction must carry one B-I, U. S. Coast Guard approved fire extinguisher.

All power boats 26 feet to less than 40 feet must carry two B-I or one B-II U. S. Coast Guard approved fire extinguishers.

40 feet to less than 65 feet must carry three B-I or one B-II and 1 B-I U. S. Coast Guard approved fire extinguishers..

Vessels over 65 feet must comply with Federal Standards.

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. 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.




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