What is a Requirement for Fire Extinguishers on a Boat?

 To answer the question “what is a requirement for fire extinguishers on a boat ” we must first understand the basics. What are the different types of fire extinguishers, what should they be composed of, what is a fixed safety system, and what do the requirements depend on. So let’s get started. 

Classes of fire:

The USCG requires specific types of fire extinguishers for marine purposes. If you don’t know about the types of fires, then here is a short overview of what you need to know: 

The following are the classes of fires that are based on the American system of classification. Depending on the region you’re in the classes may vary.

  • Class A: Consist of easily combustible material like wood and paper
  • Flammable gases and liquids are included in this class are included in class B
  • Class C: Consist of electrical fires
  • Whereas, Class D and k are related to metal fires and kitchen fires respectively

Special extinguishers are designed to combat these specific classes of fire, For example, a Class B fire extinguisher is going to be used against flammable liquids and also gases. When it comes to boats this type of extinguisher is our primary concern

Types of fire extinguishers based on composition:

Here are some of the most common types of fire extinguishers used these days. 

ABC Fire extinguishers: this type of fire extinguisher mostly uses Mono-ammonium phosphate as it’s main component, it is named so because it is effective against all three (A, B, C) classes of fire.

Halon: These types of fire extinguishers are somewhat of a rare sight these days. They have been banned, the reason behind that being their harmful effects on the ozone layer. However, they can still be found and used, they are not illegal to carry only their manufacturing has ceased. 

Carbon dioxide fire extinguisher: These types of fire extinguishers are used for Class B and C fires. As the name suggests they are composed of carbon dioxide. Carbon dioxide is one of the most commonly used fire-retardants and hence the is also the most common type of fire extinguisher to be used.

If you want to learn more about the different types of fires and fire extinguishers then be sure to check out the highlighted articles, as it will provide you with more detail. 

What are B-Ⅰ/B-Ⅱ and 5-B/20-B fire extinguishers:

The B generally indicates the class of the extinguisher and which class of fire can it be used against, marine fire extinguishers have been assigned as Class B extinguishers.


According to the USCG, a fire extinguisher can be classified as a B1 class extinguisher if it meets the following requirements. If it’s an ABC extinguisher then the fire retardant material should be 2 pounds or greater. For a carbon dioxide-based fire extinguisher, the carbon dioxide content should be more than five pounds. If it’s halon based it should be 2.5 pounds or more.


The requirements for a B-Ⅱ fire extinguisher, according to the USCG are pretty much the same as those for a B-Ⅰ extinguisher. The only exception being the quantity of fire retardants. For an ABC Fire extinguisher, you require more than ten pounds of dry powder. A carbon dioxide-based extinguisher will require 15 pounds or more. Whereas a halon based one would require 10 pounds or more.


To meet the requirements set by the United States Coast guard an ABC fire extinguisher require 2 pounds of material, a carbon dioxide-based fire extinguisher requires 5 pounds of material whereas a halon-based one requires only 2 ½ pounds.


When it comes to the 20-B fire extinguisher, the USCG follows similar guidelines to a B-Ⅱ fire extinguisher. Generally, the number indicates how many square inches can the extinguisher put out. What this means is that a 20-B one could potentially put our 20 square inches or more of the flame.

These two types of fire extinguishers are interchangeable, the USCG guidelines state that you can use a B-Ⅱ instead of two B-Ⅰ’s. One B-Ⅱ corresponds to a 20-B extinguisher and one B-Ⅰ equals a 5-B. 

Fixed fire extinguishing system:

A fixed fire extinguishing system is used to quickly identify and put ou any fires in the protected area. It is usually present in areas where there is a risk of losing valuable equipment or data. However, it is also commonly used in boats.

It consists of fire detecting devices, an alarm system, a central control panel to check and control the system, a system of tubes to transport the extinguishing material, the extinguishers themselves, and nozzles to release the fire extinguishing material. As one can expect this type of system warrants a reduction in the requirements.

Requirements for fire extinguishers on a boat?

The requirements of the USCG depend mainly on three things: the size, the presence of a fixed fire safety system, and the type of vehicle.

If the boat is small or a fixed fire safety system is present then the number of fire extinguishers is reduced or in some cases becomes zero. 

In case of Motorboats:

Motorboats that are under sixteen feet require at least one B1 (B-5) fire extinguisher. However, if the motorboat in question has a fixed fire safety system then no fire extinguisher is required.

If the boat is between 16 to 26 feet then we need one 5-B fire extinguisher and nothing is required if it has a fixed fire safety system.

Motorboats that are between 26 to 40 feet require two 5-B fire extinguishers or one in a case where a fixed fire safety system is present. Two 5-B fire extinguishers can be replaced by a single B-Ⅱ (20-B) fire extinguisher. It must be noted that only one 5-B is required with a fixed fire safety system.

Motorboats between 40 to 65 feet require at least three 5-B or one 5-B and a 20-B fire extinguisher. For a fixed system, a single 20-B will do.

In case of Motor vessels:

  • Motor vessels with a GT (gross tonnage) less than 50: They require at least one 20-B or B-Ⅱ fire extinguisher.
  • GT between 50 and 100: Require two 20-B fire extinguishers.
  • Motor vessels with a GT between 100 and 500: Require three 20-B fire extinguishers
  • GT between 500 and 1000: Requires six 20-B fire extinguishers.
  • GT over 1000: Requires eight 20-B fire extinguishers.


So hopefully now you know the answer to the question “what is a requirement for fire extinguishers on a boat ” for more details you can also check out this document on page 5. For more information regarding fire safety and firefighter, essentials are sure to check us out at firefightertools.co.

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