Fire Extinguishers – Which is Best for the Job

Chris Riley by Chris Riley Updated on July 29, 2019. In nauticalknowhow

Thanks to FS2 Gregory Berry, USCG Boothbay Harbor Maine for a detailed explanation of the different fire extinguishers available to fight certain kinds of fires. Just as a reminder:

  • Class A fires are combustible solids such as wood, fiberglass, cloth, etc.
  • Class B fires are flammable liquids such as gasoline, diesel, etc.
  • Class C fires are electrical

Portable, handheld fire extinguishers have to be USCG approved but how do you know which approved extinguisher you should use? Fire extinguishers contain different extinguishing agents and are labeled so that you know which one is best for the particular type of fire you have.

Type of Extinguisher Class of Fire Notes:

Carbon Dioxide

B, C Carbon Dioxide is a class B, C, agent only. Because of the CO2 high pressure, it is not recommended for use on Class A, amber and ash based fires. Why? Because of the hazard of spreading the fire when blasting it with the high pressure gas.
(until year 2000)
A, B, C Halon 1211 carries the A, B, C rating only in a capacity of 9 pounds. Units smaller than 9 pounds only carry the B, C rating. Halon gas vaporizes too quickly to maintain a Class A fire in small quantities.
Dry Chemical B, C Dry chemical extinguishers come in three varieties. Sodium Bicarbonate B, C (Alkaline); Potassium Bicarbonate, Purple “K”, B, C (Alkaline); and Mono Ammonium Phosphate A, B, C (Acidic). The A, B, C dry chemical is not recommended for marine use for two reasons:

  • It is corrosive
  • The way in which this agent obtains it class A rating is its ability to melt, seep and encase. This necessitates dismantling of equipment to repair or rebuild.
Foam A, B Foam extinguishers are water based and quench Class A fires. They also blanket, smother and separate the vapor layer in Class B fires.




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