BoatUS Offers “Myth-Busting” Fire Extinguisher Tips


BoatUS has released a list of 4 commonly held misconceptions about onboard fire extinguishers. Here are the myths, as well as a description of the different types of fire extinguishers available and the types of fires they should be used with.

Myth 1: Tapping or striking the extinguisher keeps the contents “fresh.”

Reality: Leave the mallet at home. Unlike days of old, today’s modern fire extinguishers don’t use chemicals that cake, get hard, or need to be broken up. Whacking it with a mallet or hammer could compromise the extinguisher’s ability to put out a fire.

Myth 2: All extinguishers must be mounted with a bracket.

Reality: Mounting a fire extinguisher on a bracket keeps the unit in a handy place and may protect it from being banged around the boat, but it is not a legal requirement. You do, however, need to ensure the extinguisher is readily accessible, so leaving it at the bottom of locker or compartment is a big no-no.

Myth 3: Fire extinguishers get old and go “bad” every year.

Reality: Unlike flares, fire extinguishers have no expiration date. To meet Coast Guard carriage requirements however, the extinguisher must be Coast Guard-approved and in “good and serviceable” condition. The charge indicator needs to be in the green zone, the nozzle free of obstruction and the cylinder not rusted.

Myth 4: The law says you only need to carry one extinguisher.

Reality: Coast Guard minimum equipment requirements dictate that larger vessels require more than one fire extinguisher. While a full list of all minimum safety gear requirements for all boat sizes can be found at, don’t let that stop you from adding additional extinguishers.

Know Your Fire Extinguisher!

  • Water extinguishers or APW extinguishers (air-pressurized water) are suitable for Class A fires only (see below). Never use a water extinguisher on grease fires, electrical fires or class D fires as the flames will spread and make the fire bigger. Water extinguishers are filled with water and are typically pressurized with air. Only fight the fire if you’re certain it contains ordinary combustible materials only.
  • Dry-chemical extinguishers come in a variety of types and are suitable for a combination of Class A, B and C fires {see below}. They are filled with foam or powder and pressurized with nitrogen.

BC: This is the regular type of dry chemical extinguisher. It is filled with sodium bicarbonate or potassium bicarbonate. The BC variety leaves a mildly corrosive residue that must be cleaned immediately to prevent any damage to materials.

ABC: This is a multipurpose dry-chemical extinguisher. The ABC type is filled with monoammonium phosphate, a yellow powder that leaves a sticky residue that may damage electrical appliances such as computers and onboard electronics.

  • Class A: For ordinary combustible materials such as paper, wood, cardboard and most plastics. The numerical rating on these types of extinguishers indicates the amount of water it holds and the amount of fire it can extinguish. Geometric symbol: green triangle
  • Class B: For fires involving flammable or combustible liquids such as gasoline, kerosene, grease and oil. The numerical rating for class B extinguishers indicates the approximate number of square feet of fire it can extinguish. Geometric symbol: red square
  • Class C: For fires involving electrical equipment, such as appliances, wiring, circuit breakers and outlets. Never use water to extinguish class C fires, as the risk of electrical shock is far too great. Class C extinguishers do not have a numerical rating. The C classification means the extinguishing agent is non-conductive. Geometric symbol: blue circle)
  • Class D: For fires that involve combustible metals, such as magnesium, titanium, potassium and sodium. These types of extinguishers also have no numerical rating, nor are they given a multi-purpose rating – they are designed for class D fires only. Geometric symbol: yellow decagon
  • Class K: For fires that involve cooking oils, trans-fats, or fats in cooking appliances and are typically found in restaurant and cafeteria kitchens. Geometric symbol: black hexagon