Fire extinguishers — classes, ratings and the required outfit

What the rule requires

Length first, then the fixed-system column

A recreational vessel 65 feet or less in length takes its minimum portable count from Table 1 of 33 CFR §175.320, which is indexed on length and gives two answers for every band: one for a vessel with no fixed fire extinguishing system in the machinery space, one for a vessel that has one. The counts are expressed in 5-B portable extinguishers.

• Under 16 feet — one 5-B; none if a fixed system is installed in the machinery space.
• 16 feet or more but less than 26 feet — one 5-B; none with a fixed system.
• 26 feet or more but less than 40 feet — two 5-B; one with a fixed system.
• 40 feet or more but not more than 65 feet — three 5-B; two with a fixed system.

One 20-B portable may be substituted for two 5-B portables, and extinguishers with larger numerical ratings or multiple letter designations may be used to meet either table.

Above 65 feet the length table stops governing. A recreational vessel more than 65 feet in length counts 20-B portables against gross tonnage: one at not more than 50 GT, two over 50 but not more than 100, three over 100 but not more than 500, six over 500 but not more than 1,000, and eight above 1,000.

That tonnage count is the vessel's general outfit. The machinery space then draws its own equipment on top of it: one 20-B for each 1,000 brake horsepower of the main engines or fraction thereof, capped at six such extinguishers however large the plant. Over 300 gross tons, the machinery space must additionally have either one 160-B semi-portable system or a fixed system. The frame or support of that 160-B is welded or otherwise permanently attached to a bulkhead or deck, and if an approved semi-portable is wheeled it must be securely stowed when not in use so it cannot roll out of control in a heavy sea. A semi-portable is fitted with a suitable hose and nozzle, or other practicable means, so that all portions of the space concerned can be covered.

A 62-foot motor yacht has an approved fixed system in the engine room. How many portable extinguishers must she carry, and what is the minimum acceptable outfit?

Length 62 feet, so the length table governs, band 40 to 65 feet, fixed-system column: two 5-B. Because one 20-B substitutes for two 5-B, a single 20-B in serviceable condition satisfies the requirement. Two 5-B units also satisfy it. The fixed system reduces the portable count; it does not remove it in this band.

Approved type, serviceable, and where it is stowed

Every portable and semi-portable extinguisher must be on board and readily accessible, of an approved type, and neither expired nor apparently used already. Serviceable condition has four specific tests under 33 CFR §175.310: a pressure gauge or indicator reading in the operable range or position, the lock pin firmly in place, the discharge nozzle clean and free of obstruction, and no visible signs of significant corrosion or damage. A boarding officer works down that list, and any one failure takes the unit out of the required outfit.

Vaporizing-liquid extinguishers containing carbon tetrachloride, chlorobromomethane or other toxic vaporizing liquids are not acceptable as required equipment at all. Separately, an extinguisher whose name plate requires protection from freezing must not be stowed where freezing temperatures may be expected.

Approved type means approved under 46 CFR chapter I, subchapter Q, with current and former approvals listed at the Coast Guard's equipment database and the cognizant OCMI available for questions on approved equipment, per 33 CFR §175.305. For uninspected vessels the same principle is stated flatly: hand portable extinguishers, semiportable systems and fixed systems shall all be of an approved type, requiring the specific approval of the Commandant, under 46 CFR §25.30-5.

Fixed installations carry their own design standards. A fixed system must be Coast Guard approved under 46 CFR part 162; a carbon dioxide system is designed and installed in accordance with 46 CFR part 76, subpart 76.15; an automatic sprinkler system in accordance with 46 CFR 25.30-15(c), all under 33 CFR §175.315.

Gauge-less dry chemical units and older vessels

Dry chemical stored pressure extinguishers without a gauge or indicating device, manufactured before January 1, 1965, may be carried on recreational vessels if maintained serviceable, and the maintenance is prescribed: reweighed ashore at intervals no greater than six months from the last weight check shown on the inspection record tag, serviced if the container weighs 1/4 ounce less than the figure stamped on it, and serviced if the frangible disc in the neck is not intact where the outer seals are broken. Dry chemical powder in the nozzle or elsewhere on the shell is evidence of damage, use or leakage, and the unit must then be serviced or replaced.

Gauge-less units manufactured after that date cannot bear the marine type label of 46 CFR 162.028-4 and may be aboard only as excess equipment.

Vessels of model year 1953 through 2017 get a narrow grandfather under 33 CFR §175.380: previously installed extinguishers with capacities below what the current tables require need not be replaced, but must be maintained in good condition, and everything installed after August 22, 2016 meets the current requirements in full. A vessel built before model year 1953 meets the applicable number and general type provisions, may keep previously approved installations in service while they remain in good condition, and must bring all new installations and replacements up to current requirement, per 33 CFR §175.390.

The exemption, and the spaces that defeat it

A vessel less than 26 feet in length, propelled by an outboard motor, need not carry portable extinguishers if the construction of the vessel will not permit the entrapment of explosive or flammable gases or vapors. Both halves apply.

The conditions that create entrapment are named: a closed compartment under thwarts and seats where portable fuel tanks may be stored, double bottoms not sealed to the hull or not completely filled with flotation material, closed living spaces, closed stowage compartments holding combustible or flammable materials, and permanently installed fuel tanks. Bait wells, glove compartments, buoyant flotation material, open slatted flooring and ice chests do not in themselves require extinguishers.

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Telling it apart — the class letters

The single criterion is the fuel that is burning, not where the fire is or what compartment it started in, under USCG Boatswain Manual Ch. 6 §6.1. The common chain is Ash, Barrel, Current, Dangerous metals, Kitchen; it carries the letters reliably and loses one detail, noted below.

• A — ordinary combustibles. Misfiled case: a mattress or dunnage fire in a closed living space called C because there is wiring in the same compartment.
• B — flammable liquids and gas. The "barrel" image implies liquid only, so a propane or CNG fire gets called something else; it is class B.
• C — energised electrical. Misfiled case: a fuel fire in the engine room called C because it is among machinery. The fuel decides the class.
• D — combustible metals, rare on small vessels.
• K — cooking oils, the galley fire. Misfiled as B because cooking oil is a liquid.

Use the extinguisher class that matches the fuel. The tables in 33 CFR §175.320 require a B rating on both counts, 5-B and 20-B, and permit larger numerical ratings or multiple letter designations, so a unit rated 20-B:C is acceptable where a 5-B is required — larger numeral, additional letter.

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Working a question

Case 1. A 44-foot inboard sportfisherman, no fixed system in the engine room. The owner has aboard one 20-B and one 5-B, both with the gauge in the green and pins intact. Compliant?

1. Take the length: 44 feet is 65 feet or less, so Table 1 governs. The tonnage table plays no part.
2. Find the band: 40 feet or more but not more than 65.
3. Choose the column: no fixed system in the machinery space, so three 5-B.
4. Apply the substitution: one 20-B counts as two 5-B, so the 20-B plus the 5-B gives three. The count is met.
5. Test condition on each unit: gauge in the operable range, pin firmly in place, nozzle clear, no significant corrosion, not expired or apparently used. Both pass.
6. Compliant. Had the vessel a fixed system in the machinery space, the requirement would fall to two 5-B and the 20-B alone would carry it.

Case 2. A 78-foot recreational vessel of 140 gross tons, main engines totalling 1,400 brake horsepower.

1. Length is more than 65 feet, so tonnage governs the general outfit, not length.
2. 140 GT falls in the band over 100 but not more than 500: three 20-B.
3. Add the machinery space allowance: one 20-B per 1,000 bhp or fraction. 1,400 bhp is one full thousand plus a fraction, so two more 20-B. The six-extinguisher cap is nowhere near.
4. Test the 300 GT threshold: at 140 GT the vessel is below it, so neither the 160-B semi-portable nor a fixed system is required in the machinery space.
5. Total requirement: five 20-B portables, all of approved type and in serviceable condition.

The error to watch in step 3 is rounding down. A vessel with 2,100 bhp needs three, not two.

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Where candidates lose the point

A 70-foot vessel gets counted off the length table because 70 feet feels close to 65 and the length table is the familiar one. Above 65 feet the length bands do not apply; the answer comes from gross tonnage plus brake horsepower.

The fixed-system column gets read as an exemption. On a 40-to-65-foot vessel a fixed system in the machinery space takes the requirement from three 5-B to two, not to zero. Only under 26 feet does that column read zero.

The outboard exemption gets applied to any small boat with an outboard on the bracket. The vessel must be less than 26 feet and built so that explosive or flammable gases or vapors cannot be entrapped. A permanently installed fuel tank or a closed living space is one of the named conditions that puts the vessel back into the requirement.

An extinguisher that is full and holding pressure but past its expiry date gets counted. It cannot be: not expired and not appearing to have been previously used are separate requirements alongside the gauge, pin, nozzle and corrosion checks.

The pre-1965 allowance gets stretched to any gauge-less dry chemical unit. It runs only to units manufactured before January 1, 1965, and only with the weight-check regime attached. A gauge-less unit of later manufacture cannot carry the marine type label and counts as excess equipment only.

"Built in 1974, so 1974 rules" is the wrong reading of grandfathering. The under-capacity units already installed may stay if kept in good condition, and every extinguisher installed after August 22, 2016 meets the current standard.

A galley fire in a deep fryer gets answered B on the strength of "oil is a liquid." Cooking oils are K.

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Check yourself

You are surveying a 34-foot recreational vessel with no fixed fire extinguishing system. She carries one 20-B in a bracket at the helm. Does she meet the minimum?

Yes. The band 26 feet or more but less than 40, no fixed system, requires two 5-B. One 20-B substitutes for two 5-B, so the single unit satisfies the count — provided it is readily accessible, of approved type, unexpired and serviceable on all four condition tests.

A 90-foot recreational vessel of 320 gross tons has three 20-B portables in the accommodation and two 20-B in the engine room for her 1,900 bhp mains. The engine room has no fixed system and no semi-portable. What is missing?

The 160-B semi-portable system. Above 300 gross tons the machinery space must have either one 160-B semi-portable or a fixed system. Her portable counts are right: 320 GT falls in the over-100-to-500 band for three 20-B, and 1,900 bhp is one thousand plus a fraction, giving two machinery-space 20-B.

An extinguisher on the required list has a pressure gauge reading in the green, a clean nozzle and no corrosion, but the lock pin is missing and the seal is broken. Can you count it toward the minimum?

No. The lock pin firmly in place is one of the four stated conditions for good and serviceable working order, and a broken seal indicates tampering or use. Replace or service it; the vessel is short one unit until then.

A 22-foot open skiff with an outboard has a permanently installed fuel tank under the after deck. Is she exempt from carrying a portable extinguisher?

No. The exemption for a vessel less than 26 feet propelled by an outboard applies only where the construction will not permit entrapment of explosive or flammable gases or vapors, and a permanently installed fuel tank is one of the named conditions requiring extinguishers. She carries one 5-B.

Fire breaks out in the engine room in fuel that has collected under a generator, with the generator running. What class of fire is it and what governs your choice of extinguisher?

Class is determined by the fuel. Burning diesel is B; the energised generator adds a C exposure. Use an extinguisher rated for the fuel involved. A unit bearing multiple letter designations is acceptable as required equipment where the numerical rating meets the table.

An owner offers a 1962-manufactured gauge-less dry chemical extinguisher, tag showing the last shore weight check nine months ago, shell weight 1/8 ounce under stamped. Acceptable as required equipment?

Not as it stands. Pre-1965 gauge-less dry chemical units are permitted, but once six months have elapsed since the last shore weight check they no longer meet required maintenance conditions until reweighed ashore and found serviceable and within weight. The 1/8 ounce shortfall alone would not condemn it — servicing is triggered at 1/4 ounce under the stamped weight — but the lapsed weight check does.

A vessel's engine room is fitted with a CO2 flooding system installed by a yard to a design of its own. Where do you look to judge it?

A fixed system must be of a type approved by the Coast Guard under 46 CFR part 162, and a carbon dioxide system must be designed and installed in accordance with 46 CFR part 76, subpart 76.15. A yard's own design that does not meet those does not count as the fixed system that reduces the portable requirement.