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Fire Extinguishers
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Types of Fires
Class A - Ordinary Combustible Materials. This includes wood, paper, cloth, rubber, and some plastics-almost anything that leaves an ash.
Class B - Flammable Liquids. This includes gasoline, oil, kerosene, diesel fuel, alcohol, tar, paint and lacquers.
Class C - Live Electrical Fires. The heat source is a live electrical circuit which is arcing or hot due to overloading. Turning off the electricity will usually result in a Class A fire.
Ratings & Requirements
Ratings reflect an extinguisher's ability to combat particular types of fires. UL (Underwriters Laboratory) uses letters to denote the type of fires the extinguisher is capable of fighting, and numbers to refer to the fire fighting "capacity" relative to other extinguishers. For example, a 1-A;10-B:C extinguisher is effective on Class A, B, and C fires, and a 40-B:C extinguisher has four times the extinguishing capacity of a 10-B:C extinguisher.
The Coast Guard has chosen to quantify extinguisher abilities differently from UL, and they use the terms B-I and B-II. The difference is that the Coast Guard looks only at the weight of the extinguishing agent, while UL looks at the fire fighting ability.
The Coast Guard requires from one to three extinguishers on pleasure boats, depending on whether they have an engine, and whether there is a permanently-mounted fixed extinguisher system in the engine room. For more information, see the chart, "US Coast Guard Minimum Equipment Requirements" earlier in this section. Like all Coast Guard requirements, these are really minimal. Buy enough to satisfy the requirements, and then address the needs of your particular boat. Remember that extinguishers are only effective if you can get to them. We recommend at least one in the cockpit, one in a forward cabin, and one in the galley area, reachable even if the stove is on fire. Legally, three small dry chemical extinguishers will meet the requirements of boats to 20 meters (65 ft.). Although individual requirement may differ, one small dry chem (B:C) or tri-class (A:B:C) extinguisher per cabin is a logical minimum, plus one accessible from the cockpit.
Portable extinguishers must be mounted in a bracket which has a strap to prevent it from falling when the boat pounds or heels. Although some plastic brackets are Coast Guard approved, we recommend beefier metal brackets for added security. "Hang type" brackets that rely on gravity are not Coast Guard approved, and should not be used.
Types of Extinguishing Agents
Water - Good for Class A fires. Extinguishers are heavy, difficult to store, and are NOT for use on flammable liquid or electrical fires.
Carbon Dioxide (CO2) - Good for Class B and Class C fires. No clean-up. Easy to use. Useful only in confined interior spaces. Does not cool fire.
Halotron 1 - Newly EPA-approved. Safe for computers, electronics, even clean rooms, and leaves no residue after use.
FE-241, FM-200 - Relatively non-toxic Halon replacements are effective on all fire classes. Not as effective as Halon. Expensive.
Dry Chemical - Low toxicity. Inexpensive. Effective on Class B and Class C fires. Not effective on Class A fires. Difficult to clean up.
Tri-Class Dry Chemical - Low toxicity. Inexpensive. Effective on Class B and Class C fires. Moderately effective on Class A fires. Difficult to clean up. Corrosive to metal and electronics; not a good choice for helm or nav station.
Aqueous Foam - This relatively new technology is extremely easy to use effectively on Class A, B, and C fires. Toxicity testing still in progress.
Source: www.westmarine.com
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