Fighting small fires on the job

BSO's Department of Fire Rescue reminds employers that federal law requires businesses with portable fire extinguishers in the workplace train employees to use them. When used properly, portable fire extinguishers can save lives and property by putting out a small fire or containing one until the fire department arrives.

In the workplace, place fire extinguishers within easy reach, so employees can access them quickly while the fire is still small. Mount them near doors so anyone using them will have a safe escape route.

Before fighting a fire in the workplace

  • Be sure an alarm has been sounded, people are leaving the building and the fire department is being notified.
  • Be sure you know how to operate your fire extinguisher and the right way to fight a fire.
  • Be sure you have an unobstructed escape route in case you can't put out the fire.
  • Know what's burning and be sure your extinguisher is capable of fighting that kind of fire. Consider the danger posed by hazardous or highly flammable materials near the fire area.

Using an extinguisher: the PASS method

When using a fire extinguisher, keep your back to an exit and, depending on the size of your extinguisher, begin by standing 6 to 8 feet away from the fire. Follow the four-step PASS procedure (Pull, Aim, Squeeze, Sweep) outlined below. If the fire does not begin to go out immediately, leave the area at once.

  • PULL the pin: this unlocks the operating lever and allows you to discharge the extinguisher. Some extinguishers may have other lever-release mechanisms.
  • AIM low: point the extinguisher hose (or nozzle) at the base of the fire.
  • SQUEEZE the lever above the handle; this discharges the extinguishing agent. For cartridge-operated dry-chemical extinguishers, follow the instructions on the extinguisher.
  • SWEEP from side to side: moving carefully toward the fire, keep the extinguisher aimed at the base of the fire and sweep back and forth until the flames appear to be out.

Remember that portable fire extinguishers discharge faster than most people think, many within 8 to 10 seconds. Have the fire department inspect the fire site, even if you think you've extinguished the fire.

Use the proper extinguisher

Fire extinguishers are tested by independent testing laboratories and are labeled for the type of fire they are intended to extinguish. There are four classes of fires and extinguishers are labeled using standard letters and symbols or both for the classes of fires on which they can be used.

A red slash through any of the symbols tells you the extinguisher cannot be used on that class of fire.

A missing symbol tells you only that the extinguisher has not been tested for that class of fire but may be used if an extinguisher labeled for that class of fire is not available.

Class A: Ordinary combustibles such as wood, cloth and paper.

Class B: Flammable liquids such as gasoline, oil and oil-based paint.

Class C: Energized electrical equipment such as wiring, fuse boxes, circuit breakers, machinery and appliances.

Class D: Combustible metals such as magnesium or sodium. Extinguishers for Class D fires must match the type of metal that is burning. These extinguishers do not use numerical ratings; the are labeled with a list detailing the metals that match the unit's extinguishing agent.

It is extremely dangerous to use water or an extinguisher labeled only for Class A fires on a fire involving flammable liquids or energized electrical equipment.

Portable extinguishers are also rated for the size of fire they can handle, a number from 1 to 40 for Class A fires and 1 to 640 for Class B fires. This rating appears on the label (for example, 2A:10B:C). The larger the numbers, the larger the fire it can handle. No number accompanies an extinguisher's C rating.

Types of fire extinguishers

Extinguishers differ by the extinguishing agent they expel onto a fire.

Pressurized water models are appropriate for use on Class A fires only. These must never be used on electrical or flammable-liquid fires.

Dry chemical extinguishers blanket burning materials with powdered chemicals. In some models, the chemicals are stored under pressure; in others, the chemicals are expelled by pressure supplied by a separate gas-filled cartridge. The dry chemicals used are corrosive and must be cleaned up immediately. ABC dry chemical extinguishers use an ammonium phosphate extinguishing agent and can be used on Class A, B, and C fires (these units aren't appropriate for fighting a fire in a commercial grease fryer because they render the fryer's automatic fire protection system ineffective). BC dry chemical extinguishers, suitable for fighting Class B and C fires, contain sodium bicarbonate (for smaller fires) or potassium bicarbonate, urea-base potassium bicarbonate, or potassium chloride (for larger fires) and are preferred for fighting grease fires (always activate a cooking appliance's own extinguishing system first).

Carbon dioxide extinguishers contain pressurized liquid carbon dioxide, which turns to a gas when expelled. These models are rated for use on Class B and C fires, but never hesitate to use carbon dioxide extinguishers on a Class A fire. Carbon dioxide residue is not corrosive.

Foam (or AFFF and FFFP) extinguishers blanket the surface of a burning flammable liquid, "smothering" the fire by denying it oxygen. Since the foams are mostly water, which conducts electricity, foam extinguishers cannot be used on electrical fires.

For more information on fire extinguishers or selecting the appropriate extinguisher for your business, contact your local fire agency or BSO Fire Rescue.

Translate This Page: