Fire at Sea

Fire Suppressants & Extinguishers

What Types are Available?

Fire Suppressants - A fancy term for the agents found within fire extinguishers that actually interact with the fire to extinguish it.

Below is a generic list of currently available fire suppressants:

Clean Agents
Dry Chemical
Dry Powder

Wet Chemical
Water Mist

Halon SystemsClean Agents: The primary use of "Clean Agent" suppressants (Halon, Halotron, et al.) is when sensitive equipment such as electronics or operating machinery require protection. Clean Agents typically provide a non-conductive suppressant that leaves no residue.

Clean Agents extinguish fires by interrupting the "Chemical Reaction" element and/or removing the "Heat Element" from the fire tetrahedron. Clean agent extinguishers are effective on Class A, B and C fires. However, smaller sized handheld extinguishers are not large enough to effectively combat a Class A fire so are only rated for Class B and Class C fires. As a rule of thumb only "Clean Agent" extinguishers with a capacity of 8 lbs. or more are rated for a Class A fire.

While expensive, Clean Agents are perfect for fixed fire suppression systems for engine room’s onboard vessels.CO<sub>2</sub>

CO2 (Carbon Dioxide): Is primarily used for Class B and C fires. They remove the Oxygen Element as well as removing the Heat Element due to the very cold discharge of expanding gas. They are generally considered to be ineffective on Class A fires.

Dry Chemical: (Be Careful Here!) Many mistakenly consider Dry Chemical and Dry Powder fire suppressants to be the same thing. They are not!

Dry ChemicalDry Chemical extinguishers are the most common found in use in the U.S. both ashore and afloat.

Dry Chemical extinguishing agents work by breaking down the Chemical Reaction portion of the tetrahedron while also creating a barrier between the Fuel Element and the Oxygen Element.

Dry Chemical suppressants come in two varieties: Multi-Purpose Dry Chemical and Ordinary Dry Chemical. Multi-Purpose Dry Chemical is effective against Class A, B, and C fires while Ordinary Dry Chemical is for use on Class B and Class C fires only. You need to carefully read the label.

Dry Powder

Dry Powder: Fire suppressants are similar to Dry Chemical, but they work differently by placing a barrier between Fuel Element and the Oxygen Element and to a much lesser extent removing the Heat Element of the tetrahedron.

The important difference to remember is that Dry Powder suppressants are only used for combustible metal fires (Class D). They are ineffective on Class A, B, C, and K fires.


Foam: works by removing the Heat Element and has the ability to separate the Fuel Element and the Oxygen Element of the Tetrahedron.

These type of extinguishers are primarily designed to fight Class A fires. Fighting Class B fires with foam while effective, should be left to the experts. Never use Foam suppressants on Class C electrical fires.

Wet Chemical

Wet Chemical: suppressants are a relatively new. They work by removing the Heat element of the fire tetrahedron while preventing re-ignition by creating a barrier between the Oxygen and Fuel Elements.

They are primarily designed for use in Class K fires however, some may be effective for Class A fires.

Water Mist (De-Ionized) as a suppressant is another relatively new development. Like Water, they work by reducing the oxygen levels and removing the Heat Element of the tetrahedron. Reportedly, they are an alternative to Clean Agent suppressants in preventing residue contamination.

They reportedly can be used against Class A, B, C, and K fires. Forgive me, but putting water of any kind on an energized electrical circuit of a Class C fire, kind of raises some concerns in my mind.

Bucket of Water

Water is effective in removing the Heat Element of the Tetrahedron. Basically cooling the fire to below its ignition temperature. It is primarily used for Class A fires.

As a general rule, water should not be used on Class B fires. However, water, when used by those specifically trained in its application on flammable liquids can be effective. It should never be used on Class C Fires.

U.S.C.G. Approved Fire Extinguishers

There Has Been Some Changes

The old system of B-I and B-II fire extinguishers is a thing of the past. On 22 July 2016, the U.S. Coast Guard implemented new standards in regards to Fire Protection, Detection, and Extinguishing Equipment.

The changes have brought the Coast Guard’s regulations in line with that of the "National Fire Protection Association’s" (NFPA) standards. This change is for portable and semi-portable fire extinguishing equipment only and pertains to both inspected and uninspected vessels. Every fire extinguisher must still carry a Coast Guard Approval Number which now certifies only the bracket used to mount the fire extinguisher. Lastly, it does not change or affect fixed fire extinguishing systems including CO2.

So What are all these New Numbers?

If you are familiar with the NFPA fire extinguisher standards, then this new coding system will be old hat. For those not familiar with the NFPA system, read on...

First a couple of examples of the new coding system which is shown on the label of all fire extinguishers:


The Letters

To begin, all "Letters" shown in any code indicate the class of fire that the extinguisher is designed for. In the case of the above codes:

The first code above - (5B:C)) indicates the extinguisher is designed to fight Class B and C fires only.

The second code - (1A:10B:C) indicates the extinguisher is designed to fight Class A, B, and C fires. It is also commonly referred to as a "Multi-Purpose" fire extinguisher.

You may see other codes such as "20B:C" indicating that the extinguisher is for Class B and Class C fires only. Likewise a code of "2A:K" means Class A and Class K fires only.

As you can see the "Lettering" portion of the code is actually pretty simple to interpret. It is the "Numeric" portions of the code that are often confusing to many.

The Numbers

The "Numbers" in the classification codes are indicative of the sizes (Size Ratings) of fires that the extinguisher is capable of fighting (more about this later). Size ratings are only shown for Class A and Class B fire extinguishers. There are no size ratings for Class C, D, or K extinguishers.

Here is how to interpret the "Numbers"...

First, the number preceding the "Letter A" (Class A fires) refers to "Water Equivalency" and the number preceding the "Letter B" (Class B fires) indicates sizes in "Square Feet." There will never be numbers preceding the "Letters C, D, or K" class designators.

In the case of Class A fires, each numeric unit is equal to 1¼ gallons of water equivalency. Using the example above, the "1A" indicates that the fire extinguisher agent is equal to 1¼ gallons of water.

Each whole integer increase in the number indicates another 1¼ gallons of water equivalency. A fire extinguisher marked "2A:5B:C" would tell you that the contents are equal to 2½ gallons of water. while "3A:5B:C" equals 3¾ gallons of water equivalency and so on….

You may often see codes such as "10B:C" where there is no "Letter A" in the code. This simply indicates that this particular fire extinguisher is not approved for use against Class A fires.

Finally, the number preceding the "Letter B" - is also a size rating based on the number of square feet of flammable liquids the fire extinguisher is rated for. Again, using the example (1A:5B:C), indicates that the fire extinguisher is capable of fighting a Class B fire 5 ft2 (five square feet) in size.

On the offhand chance that you may want to test yourself!


The answer can be found on the bottom of this page.

U.S.C.G. Fire Extinguisher Requirements

The U.S. Coast Guard has the authority to dictate required safety equipment aboard U.S. vessels. This authority includes fire extinguisher types and there sizes.

As a general rule, the U.S. Coast Guard requires every vessel to have at least one (1) Underwriters Laboratory (UL) approved fire extinguisher onboard of a specific size. The larger the boat the more you will be required to carry.

For recreational vessels, Coast Guard approved fire extinguishers are hand-portable and they must have a gauge indicating their status and be mounted in an approved marine type mounting bracket.

USCG Minimum Requirements

In accordance with 46 CFR 25.30 (Subchapter C):

Vessel Size Requirement # w/No Fixed System # w/A Fixed System
<16 Feet 5B:C 1 0
16 - 26 Feet 5B:C 1 0
26 - 40 Feet 5B:C 2 1
40 - 65 Feet 5B:C 3 2
One (20B:C) fire extinguisher may be substituted for two (5B:C) fire extinguishers.

You should keep in mind that these are the MINIMUM requirements. You should carefully evaluate your boat to determine if more should be carried.

In Closing...

Although you didn't ask, I will offer my thoughts on the subject: A fire extinguisher should be carried in every living space aboard a vessel. This would include every stateroom, salon, and galley area. Additionally a fire extinguisher for use (not kept) in the engine room and one kept in the cockpit or interior steering station. As far as sizes go 1A:5B:C for the Staterooms, a 1A:5B:C for the Salon, 1A:5B:C for the Galley, 10B:C for use in the Engine Room, and a 2A:20B:C kept in the cockpit or steering station.

Every boat is different; crew abilities, accommodation layouts, engine room locations. You need to evaluate your boat to determine what works best for you.

I understand that it is distasteful to most to have fire extinguishers hanging all over a $300k+ boat. So get creative! The requirements are only that they be accessible! Just keep in mind, it would be a good idea to ensure that everyone knows there locations.

Answer: Multi-Purpose Class A, B, and C fire extinguisher containing 5 gallons of "water equivalency" for Class A fires and capable of extinguishing a Class B fire of 20 square feet and can also be safely used on energized electrical circuits and equipment.

Compass RoseComing Soon - Fire at Sea - Part III

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