Prevent an Onboard Fire

A fixed extinguisher in your engine compartment will nip most blazes where they start. From "Hands-On Sailor" in our November 2008 issue

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Make sure this doesn’t happen to you with a few tips on fire prevention. Courtesy Of Boat U.s./ Photo By Keith Nickerson

When it comes to on-the-water sailing calamities, there are thankfully but a few that can be called catastrophes. Flooding, of course, is one; being run down by another vessel counts, too; but it’s difficult to deny that fire is just about as bad as it gets. In possession of a life raft or a life jacket, you have a chance of surviving disasters of the watery variety. There’s not much you can do, though, in the face of burning fiberglass resin or diesel fuel.

Fire extinguishers are your best defense in the face of an onboard fire, but I think prevention is even better. Still, portable fire extinguishers have two drawbacks: They must be used by a crewmember in very close proximity to the fire, and they must be set off manually. That is, they only work if activated by a person, and that person must act quickly enough, discharging the fire-extinguishing agent properly, for it to be effective.

Fixed engine-compartment fire extinguishers, on the other hand, provide an automatic method of combating a fire in the space where so many blazes typically get started.


A fixed system consists of nothing more than a metallic cylinder, often referred to as a bottle, which contains a gaseous “clean” fire-extinguishing agent. The agent is typically FM-200 or FE-241; the former possesses a low enough toxicity to be used in normally occupied spaces. These replace Halon, which, while effective, is no longer available because it depletes ozone.

The cylinder’s nozzle often incorporates a glass vial containing a liquid that expands when exposed to heat until it breaks the glass. When the glass shatters, usually near 175 F, it allows a valve to open, discharging the gas inside in a fraction of a second. The gas is clean and leaves no residue of the kind that remains after a dry-chemical extinguisher is used. The power of the released gas can damage mechanical and electrical equipment.

A worthwhile option that’s available with nearly every fixed system enables a crewmember to manually discharge the contents of the bottle at the first sign of fire, rather than waiting for automatic discharge to occur. Imagine that you see smoke drifting out from around the main engine-compartment access hatch or the cockpit locker. With a manual dischargeable system, you can pull the safety pin, yank on the handle-usually a red T handle located near the helm or in the saloon-and discharge the bottle without delay. If it turns out to be a false alarm, there’s no harm done-other than the cost of refilling the bottle-because the gas won’t damage an engine or gear.


However, whenever the system is discharged, the engine, generator, and ventilation blowers should be shut down immediately to maximize the effectiveness of the extinguisher. For the ultimate in fire protection, an optional relay box is available for use with most fixed fire-extinguishing systems. This device immediately shuts down all air-breathing equipment-engines, generators, blowers-as soon as the system discharges.

Steve D’Antonio contributes regularly to CW and offers services for owners, boatbuilders, and others in the marine industry through Steve D’Antonio Marine Consulting (www.steved