Be Ready if a Blaze Breaks Out

"Fire!," like the cry "Crew overboard!," is a warning no sailor ever wants to hear. "Hands-On Sailor" from our November 2010 issue

November 10, 2010

fire fighting 368

Marianne Lee

The disappearance of the artfully cursed gasoline auxiliary engine and the end of the era of the pressurized alcohol galley stove have improved the chances for avoiding a fire on board a sailboat. But at the same time, the addition of massive DC-power systems, propane stoves, and fuel tankage equivalent to that of a motorboat has upped the ante when it comes to a galley flare-up or an electrical short-instigated fire getting out of control. Small fires can become all-consuming conflagrations in an alarmingly short period of time. The science says it all: A fast-growing fire doubles in size every 30 seconds.

The best risk management is based upon reason, and it’s why every skipper needs to consider the prospect of fire breaking out on his vessel and how those on board should respond. These what-ifs that arise from such introspection will lead to more data gathering and a plan of action that needs to be shared with the crew. Statistics show that though fires infrequently occur on cruising sailboats, their effect can be devastating. The U.S. Coast Guard and the American Boat & Yacht Council wisely see the threat as very real, and they’ve put out regulations and recommendations that spell out both how certain systems should be installed and what firefighting equipment is mandatory.

Heat, fuel, and oxygen are the rudiments of combustion; if any one of these is removed, the blaze is extinguished. As with all elegantly simple explanations, this information is often ignored until it’s too late. For example, a small two-pound dry chemical fire extinguisher in either the hands of an expert or an amateur about to succumb to the fight-or-flight reflex has only about eight to 12 seconds of firefighting potential once the trigger lever is depressed. In the heat of the moment, many an untrained amateur has expended the vaporized dust on the flames leaping high from the burning surface rather than spreading the extinguisher’s limited contents on the base of the flames, where it will have the best results. The latter approach smothers the fire by creating a barrier between the fuel and the oxygen.


Understanding the Equipment
Fires are broken up into three classes based upon their combustion profile. Wood, paper, and other natural and synthetic fiber fires that leave an ash residue are typed as a Class A, and are best extinguished by lowering their temperature via flooding with water or aqueous foam. That’s also good reason to consider a high-pressure, high-volume water system with a sink hose and spray head or a second in-cabin tap and hose linked to a powerful deck wash-down pump to be firefighting allies.

Meanwhile, fire extinguishers may be your first line of defense for Class B and Class C fires, but an extinguisher’s operational time is short, and even a few well-placed buckets of water may save the day once the eight- to 12-second operational lifespan of a dry-chemical extinguisher is over.

Flammable liquid fires (Class B), typified by gasoline, diesel, or alcohol, are best tackled by smothering the flames with a fire blanket or oxygen-blocking extinguisher agent. Dry chemical, foam, CO2, Halotron, and other non-toxic Halon replacements all do the job. All dry chemical extinguishers should be removed from their bracket and inverted every month or so in order to keep the contents from solidifying. Also worth a mention is the inferior nature of most flimsy, mild-steel brackets that come with extinguishers. Spending some time or money on improving how these vital safety tools are housed is worth the expenditure. In addition to the extinguisher near the galley stove, reachable even if the appliance is ablaze, there should be an extinguisher in a cockpit locker and one near the skipper’s berth.


The table “Extinguishers and Their Uses” (see below) describes the types of extinguishers available. Built-in systems, such as those offered by Fireboy, can flood the engine room with an oxygen-blocking gas that can stop a blazing fuel fire in its tracks. But those who install such systems need to keep in mind that what kills a fire can also impact human respiration. Some years ago a friend of mine accidentally engaged a fixed, CO2 fire-suppression system while he was in the engine room of his boat; the gas quickly rendered him unconscious, and his wife, responding to his plight, succumbed to the same asphyxiation. Both died in the mishap.

This tragedy underscores the need to realize that limiting oxygen to quell a fire is tricky business. On one hand the rule of fire fighting is to close hatches and ports in order to lessen the air inflow. But the crew also must recognize how dangerous oxygen depletion, acrid smoke, and toxic fumes in a closed up boat can quickly become a lethal atmosphere. Compressed liquid extinguishers that emit a gaseous cloud in a confined space such as an engine compartment vary in toxicity according to their suppression agent. Some systems use FE-241 that’s meant for dispersal in an unoccupied space, while others use HFC-227ea, a gas that’s safe if occupants are still in the cabin fighting a spreading fire.

The ideal answer is to prevent a fire in the first place, or barring that good fortune, have a quick-response plan ready so you’ll be able to douse flames before they can spread. Many built-in fire suppression systems have a heat-melting auto discharge capability, but it takes either direct proximity, a very hot fire, or the ambient temperature to rise to 179 F for the system to auto deploy. By installing a manual-release cable, a crew can preempt the wait and choke off the flames before the fire builds.


Not only does opening a door or hatch to the engine compartment raise the risk of being scorched by flames; it also introduces more oxygen to a hungry fire. A built-in fire suppression system on even a modest-sized boat makes sense. It also keeps the crew from fighting an engine room fire with a dry chemical extinguisher, many of which are not very effective on Class A fires, and if the powdery, abrasive agent is ingested into a running diesel engine, it’s usually fatal to the engine itself.

Take note: Though diesel fuel may be readily abundant, engine-room fires are often a Class C blaze, one that’s linked to electrical ignition. Turning off the main battery bank switches is step one in combating this type of fire. If the current is not eliminated from the short circuit, the fire will continue despite the introduction of extinguisher agent. With this need in mind, it’s always a good idea to make sure that the main switches are not hidden away in the engine room or placed in another area where they are likely to be quickly engulfed in flames.

Fighting a Fire
Responding to a fire aboard a sailboat is similar to coping with a large hole punched in the hull. Both require immediate action and neither is forgiving to an ineffective response. At the same time that the crew confronts the all-consuming challenge of stopping the blaze or significant leak, they need to be prepared to cut their losses and be able to instantaneously switch to an abandon-ship escape plan. Knowing when to make the call is both a tough decision and a reality that’s shaped by the surroundings. One thing’s sure: Waiting a little too long can be a big mistake.


A well-prepared crew understands the chaos factor that intrudes on such disasters. They realize that their best chance for success is already in place, and it includes the fire suppression system they installed months or years ago and the extra extinguishers waiting in easily accessible locations. Even more important has been the training that the skipper has done with the crew and how each person has tested her extinguisher operation skill. They are prepared to aim the suppression agent on the base of the flames. If there are enough crew on board, one member may be assigned to communicate a Mayday, set off the EPIRB, and ready the abandon-ship gear and life raft. Others head the boat downwind to keep flames from engulfing the cockpit and hindering raft deployment if the need arises. In short, a fire grows exponentially, and there’s only a short window of time to get it under control. It takes quick response and gear at the ready to outwit the combustion triangle, and every second counts.

Take Stock on Your Boat
One of the best ways to determine how much of a fire hazard your own boat poses is to do a simple analysis of the combustible content of the boat. Tally up the major materials used to build the vessel. At first it may seem reassuring that glass fiber and lead won’t burn, but the resin that makes up 50 percent of the FRP structure will self-ignite at about 880 degrees F and burn to a crisp, creating a toxic cloud of harmful gasses.

So will the core material and most of the wood and plastic liners that stylize the interior of your vessel. Add flammable diesel fuel, combustible sails, the dodger, and the bimini and one begins to get anxious over the fact that it’s easier to list what won’t burn than what will. Also note that just one candle produces a laminar diffusion flame that can reach 2,500 F, more than enough to instigate a roaring blaze.

The galley and the engine room are the two obvious concerns; it’s why the A.B.Y.C. spends an inordinate amount of time on electrical-, fuel-, and propane-system specifications. By preventing fuel and L.P.G. leaks and lessening the chance of an electrical short, the potential for a fire goes way down.

The same consideration needs to be given to where flares and volatile chemicals like paint solvents and gas for the dinghy’s outboard are secured. Using a large propane locker as a combined storage area for gasoline and solvents is just the type of situation to avoid. Commingling explosive and flammable products may seem like a sensible approach, but with electrical wires leading to the L.P.G. solenoid and the moist, salt-laden environment that’s inside most propane lockers, these are anything but a sensible seagoing Hazmat container.

Many sailors see 12-volt DC batteries as a benign energy source with no electrocution worries. The latter is true, at least up until an inverter is wired into the system, but the former disregards the high-current and heavy-gauge circuits associated with low-voltage wiring that poses the potential for extreme heat generation if an unanticipated short circuit occurs.

Lastly, beware of the unexpected. A couple of years ago, a transatlantic passagemaker explained how a sheeting snafu turned into a fire on board. He said he’d been motorsailing in a light breeze and had trimmed the mainsheet using an electric cockpit winch, then went below to heat some water for tea. A malfunctioning solenoid switch connected to the self-tailing winch that held the mainsheet re-engaged on its own, and the noise of the engine prevented the skipper from hearing the sound of the winch coming to a stop under full load. The now non-rotating winch melted its motor-winding insulation and short circuited. A high-amperage fuse was able to carry more current than the wire that ran to the winch, which turned into a red-hot copper filament that set the liner on fire. The skipper responded, effectively switching off the current and dousing the flames with a fire extinguisher. He never expected such an incident to occur, but he knew how to effectively respond to a Class C fire. Would you?

Ralph Naranjo is a veteran mariner and Safety-at-Sea instructor.

Extinguishers and Their Uses

Types Fire Class Agent Portable or Fixed
(see table below)
Dry chemical B,C Powder P
Tri class A,B,C Powder P
Halotron A,B,C Gas Both
HFC 227ea A,B,C Gas F
FE-241 A,B,C Gas F
CO2 B,C Gas Both
Foam A,B,C Liquid Both
Water A Liquid Both

Three Classes of Fire

Fire Type Description Materials Involved
Class A Combustion leaves an Wood, cloth,
ash residue paper, etc.

Class B A liquid fuel-based fire Oil, gas, alcohol,
paint, solvent

Class C A fire started by an Wire, insulation,
electrical current electrical component

Source: Ralph Naranjo


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