Fire on a boat is bad news. If you have fire in your house on land, you can leave, you can get out and let the fire department take care of it. You may lose possessions and that’s certainly painful (I do not mean to minimize true trauma here), but if your smoke detector works and you can get out in time you’ll be all right. Out on the water it’s different. If you get a fire out there, there’s nowhere to run, nowhere to go, you have to hang in and fight it. In addition to the problem that the material of the boat itself is fuel for the fire (wood and fiberglass burn very well), fiberglass has the additional contribution of highly toxic combustion products in the smoke. Usually fire afloat involves gasoline or diesel and that makes it worse. I’ve read that a half a teacup of gasoline, mixed with a volume of air fifteen times that, has enough energy to destroy a good sized yacht. Yes folks, this is serious stuff. Viking funerals aside, fighting a fire afloat is not a pleasant place to be. Just remember if you have to use a fire extinguisher to aim the nozzle at the base of the flame because that’s where the oxidation is taking place.
There are three things a fire needs in order to burn: heat, oxygen and fuel. This mean that very basically there are three ways to put a fire out and that is to deprive it of one of the things it needs to burn. Those three ways are reflected in the basic ABC fire extinguishers you can buy at your local hardware store or chandlery.
Taking the Heat Away
Pouring water on a fire that is wood or paper based (or hitting it with a water charged fire extinguisher) cools the fire, drawing the heat out of it by the water’s change of state from liquid to steam. No heat = no fire.
Taking the Oxygen Away
Foam fire extinguishers cover burning liquids and keep oxygen away. They are only good for liquid fires and when you spray the foam on the surface of the burning liquid it makes a helluva mess. It’s like when you have a grease fire in the kitchen: first clap the lid on the pan that’s flaring up and then turn the stove off. That takes away the oxygen and the heat. Carbon dioxide fire extinguishers blanket the fire with CO2, depriving it of oxygen. By the way, it’s advisable to use a CO2 fire extinguisher on an electrical fire because water might get you electrocuted and powered chemical fire extinguishers make an awful mess. It’s not a good idea to use a CO2 extinguisher in a small enclosed space, though, because it might well deprive you of the oxygen you need to live. Just a small firefighting tip. Large vessels (I used to design firefighting systems for commercial tankers) nowadays have unmanned engine rooms and thus can have CO2 systems which will flood the entire engine room if there is a blaze. No oxygen = no fire.
Taking the Fuel away
Depriving a fire of fuel is trickier, but that’s the reason that at the local gas mart there is a station with emergency valves, so the attendant can cut off the flow of gasoline to the pumps if someone is stupid enough to use their cell phone or smoke at the gas pump. On commercial tankers there are, of course, more isolation valves than a dog has fleas. On a smaller boat there is supposed to be a valve around or under the fuel tank to shut off the flow. It’s a good idea to know where this valve is, even if you’re a guest on board. The life you save may be mine. No fuel=no fire.
One More Way
Dry chemical fire extinguishers fight the fire by one more method. Fire is a chemical process called oxidation. It does very rapidly what oxygen does to steel, so in a kinda sorta way when steel rusts it’s actually burning verrrry verrrrry slowly. Flammable (or Inflammable, oddly enough the words mean the same thing) substances like gasoline, diesel fuel, fiberglass, wood, paint, rubber, etc oxidize at a much higher rate. That’s fire. When you spray dry chemical on a fire it not only has a blanketing effect, but the chemical somehow (I don’t know the intimate chemistry of it) interrupts the oxidation process on the molecular level. I know it sounds like PFM (pure fricking magic) but it’s true.
Afloat the best approach is to ensure that a fire doesn’t get started in the first place. The photo at the beginning of this post was started while the people were not on board, and originated in the galley where they had been having problems with the auto spark lighter on the propane galley stove. So if you have any heat generating equipment on board, make sure it’s in proper working condition because chances are you won’t be as lucky as they were. One way to minimize the probability of fire afloat, if you have an inboard engine in an engine compartment, is to turn on the ventilation blowers for at least five minutes before you start the engine. This will eliminate any gasoline or diesel fumes that have been collecting in the engine compartment. So if you go skiing with friends who have an inboard engine watch carefully to see if they do this.
I’m sorry if this one has been a long post. Sorry about that. It’s just that I used to design firefighting systems for commercial tankers back in my former incarnation. I’ve read a lot of incident reports from NFPA that scared the hell out of me and the information came flooding back faster than I intended.
Take care and safe boating.