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Fire extinguisher maintenance

Jan 1, 2003

To the editor: I read with interest Chuck Husick's excellent article on fire extinguishers ("Fighting Fire," Issue 119, Jan.⁄Feb. 2002). Since I lead the training on fire extinguishers where I work, I thought some of the following information may be of interest as a follow-up to his article.

I work at an industrial plant, and we have strict internal policies that mimic the various federal and state regulations that cover the periodic inspections and maintenance of portable fire extinguishers.

Husick's article does a good job of giving an overview of the various types of extinguishers and the advantages and disadvantages of each type. However, two things caught my attention. One was a statement that dry-chemical fire extinguishers "require no service, other than an occasional shake to loosen the powder and a check of the pressure gauge to ensure that it is indicating in the green arc." Husick also didn't cover the maintenance requirements for other types of extinguishers.

Periodic shaking of a dry-chemical extinguisher is always a good idea and is recommended even for dry-chemical fire extinguishers that are on land. The naturally occurring packing of the powder can only be compounded on a vessel that is occasionally subjected to the rigors of the waves. If the powder becomes tightly packed within the cylinder, some of it may not be expelled during its discharge, limiting the usefulness of the extinguisher. More important though, all types of fire extinguishers that utilize pressure as a propellant to expel the fire extinguishing media — be it water, foam carbon dioxide or Halon — require periodic maintenance, including hydrostatic testing of the cylinder. (Hydrostatic testing involves filling a cylinder, such as a fire extinguisher or scuba tank, with a liquid, usually water, and then increasing the pressure, usually to 1.5 times the normal working pressure of the cylinder and holding it at that pressure for a period of time, i.e., 30 seconds.)

To confirm this, I searched the various Codes of Federal Regulations (CFR) that cover boating, namely CFR 46 and CFR 33, some of which concern commercial vessels and not necessarily recreation craft. I found only the requirement to visually inspect fire extinguishers annually to ensure that the seal is not broken and to ensure the gauge is in the green sector.

Not being satisfied that this was the only requirement, I then referred to the American Boat & Yacht Council Project A-4 "Fire Fighting Equipment." Appendix 5.4 covers the maintenance of portable fire extinguishers. It states that fire extinguishers should be visually checked monthly for pressure and damage, etc. But it also states that fire extinguishers should be hydrostatically tested as per NFPA (National Fire Protection Association) 10, which is what we, as an industrial plant, must do and what I had expected the CFRs to state.

I also checked NFPA 302 "Fire Protection Standard for Pleasure and Commercial Motor Craft." It too states "that fire extinguishers should be checked several times a year for damage, corrosion, tampering, etc., and that the gauges on dry-chemical extinguishers of the stored pressurize type should be checked that it is within its operating limits." It goes on to state, "Portable fire extinguishers should be maintained per 10."

Below is an excerpt from NFPA 10 listing the frequency for hydrostatic testing:

Dry-chemical with stainless steel shells:

5 years

Carbon dioxide:

5 years

Dry-chemical stored-pressure with mild steel shell, brazed brass shells or aluminum shells:

12 years

Dry-chemical cartridge operated with steel shells: 12 years

Halogenated agents: 12 years

Dry-chemical stored-pressure with steel shells: 12 years

The vast majority of portable fire extinguishers that I see on recreational craft are of the dry-chemical stored-pressure type with aluminum shells.

NFPA 10 states that stored-pressure portable fire extinguishers that have to be hydrostatically tested every 12 years shall be emptied every 6 years.

I realize that both NFPA and ABYC are basically just guidelines, not regulations, but the bottom line is that to ensure they will function as intended, all fire extinguishers, whether dry-chemical, carbon dioxide, Halon or any other that relies on pressure to expel the extinguishing agent, should be visually inspected often and should be maintained and hydrostatically tested at least as often as stated in the NFPA 10 guidelines. Additionally, extinguishers that expel vaporizing liquids, such as carbon dioxide and Halon, must be weighed to ensure that the contents have not leaked out. Vaporizing liquids will indicate on a pressure gauge the same amount of pressure until the cylinder is almost empty. So pressure gauges are not a true indicator of state of charge for this type of extinguisher.

For anyone who has never used a fire extinguisher, it is a good idea to practice on a controlled fire prior to sending it in for inspection because the inspection facility is only going to discharge the extinguisher anyway.

The proper way to use the extinguisher is to pull the pin, hold the extinguisher upright and aim the nozzle at the base of the flames. Squeeze the handle at a safe distance from the fire, say 10 to 15 feet. Sweep the nozzle slowly and methodically back and forth across the base of the flames. Begin to approach the fire slowly as it diminishes in size. Do not run rapidly towards a fire. Be careful that the velocity of the extinguishing media does not splash a flammable-liquid fire, potentially spreading it. Try to avoid putting the fire between yourself and the exit, and never turn your back on an extinguished fire — until the material has cooled substantially, there is a potential it may rekindle and flash back.

John Cattuna Jr. is a professional engineer in the State of North Carolina, a Coast Guard master upon near coastal waters, holds a full certificate in the U.S. power squadron and is a marine surveyor.