Fire Extinguishers (PASS)

A portable fire extinguisher can put out a small fire in seconds, but only if it’s the right type, it’s charged, it’s where you can reach it, and you know how to use it. Most extinguishers empty in 10 to 20 seconds, so there’s no time to read the label once the fire starts.

• Construction
• General Industry
• Home

How fire works

A fire needs four things: fuel, heat, oxygen and the chemical chain reaction that keeps it burning (the “fire tetrahedron”). Every extinguisher works by taking away one or more of these. Water cools the fuel. Carbon dioxide pushes away oxygen. Dry chemical interrupts the chain reaction and smothers the fuel. That’s why the wrong extinguisher can fail or even make a fire worse: water on a grease or gasoline fire spreads the burning liquid, and water on live electrical equipment can shock you.

Fire classes

Lithium-ion battery fires are a special case. A small extinguisher may knock down the flames, but a battery in “thermal runaway” can reignite again and again. Get away from the smoke, which is toxic, and call 911. See Battery Safety.

Types of extinguishers

Reading the label

Every listed extinguisher has a rating like 2-A:10-B:C. Here’s what it means:

• The number before A is how much Class A fire it can handle. Each “1-A” is roughly equal to 1¼ gallons of water, so a 2-A unit is about as effective as 2½ gallons of water.
• The number before B is the approximate square footage of a flammable liquid fire a non-expert can put out. A 10-B unit can handle about 10 square feet.
• C has no number. It means the agent doesn’t conduct electricity.

The label also shows the operating instructions, the agent, the date of manufacture and the service tag. A bigger number means more firefighting power. A common 5-pound ABC unit is often rated 2-A:10-B:C, and a 10-pound unit is often 4-A:60-B:C or larger.

How to use it: PASS

1. Pull the pin. Twist it to break the plastic tamper seal.
2. Aim the nozzle low, at the base of the fire, not at the flames or smoke.
3. Squeeze the handle slowly and evenly.
4. Sweep side to side across the base of the fire until it appears to be out.

• Start about 6 to 10 feet away (closer for CO₂) and move in as the fire shrinks.
• Keep your back to an exit, and stay low if there’s smoke.
• Watch the area after the fire is out. Fires often flare up again, especially with liquids and smoldering materials.
• If the extinguisher empties and the fire isn’t out, leave immediately.

Fight it or get out?

Your life is worth more than any building or piece of equipment. Only fight a fire if all of these are true:

• The alarm has been sounded and someone is calling 911
• You’ve been trained, and your employer allows employees to use extinguishers
• The fire is small and contained, about the size of a wastebasket, and isn’t spreading
• You have the right type of extinguisher, and it’s charged
• You have a clear exit behind you that the fire can’t block
• The area isn’t filling with smoke, and there are no gas cylinders, fuel tanks or explosives the fire could reach

If any answer is no, get out, close doors behind you to slow the fire, pull the alarm, call 911, and go to your muster point. See Emergency Action Plans.

What OSHA requires

Construction (29 CFR 1926.150)

• At least one extinguisher rated 2-A or higher for each 3,000 square feet of building area, with a travel distance of no more than 100 feet to the nearest one.
• At least one 2-A extinguisher on each floor. In multistory buildings, at least one next to a stairway.
• An extinguisher rated 10-B or higher within 50 feet of anywhere more than 5 gallons of flammable or combustible liquids or 5 pounds of flammable gas are being used.
• Extinguishers must be inspected and maintained according to NFPA 10. Carbon tetrachloride and other toxic vaporizing-liquid extinguishers are banned.
• For welding, cutting and other hot work, suitable fire extinguishing equipment must be ready for instant use. See Hot Work Permits.

General industry (29 CFR 1910.157)

• Extinguishers must be mounted, located and identified so they’re easy to reach. Travel distance is generally 75 feet or less for Class A and 50 feet or less for Class B hazards.
• If employees are expected to use extinguishers, the employer must train them when they’re hired and at least once a year.
• Some employers choose a total-evacuation plan instead, where nobody is expected to fight fires. Know which kind of plan your workplace has.

Inspection and maintenance

Monthly visual check:

• It’s in its assigned place, mounted, and not blocked or hidden
• The pressure gauge needle is in the green
• The pin and tamper seal are in place
• No dents, rust, leaks, or cracked or clogged hose and nozzle
• The label and instructions are readable and face outward
• The service tag shows annual maintenance within the last 12 months
• For dry chemical units, the powder isn’t packed solid (follow the manufacturer’s guidance)

Jobsite tips

• Mount extinguishers near exits and stairways so you move toward safety to get one.
• Keep one at every hot work location, fuel storage area, temporary heater and generator.
• Keep one in every company truck and on heavy equipment, and secure it so it can’t become a projectile.
• Report used, missing or damaged extinguishers right away so they’re replaced.
• Practice with a training extinguisher or fire simulator if your employer offers it.

• Don’t hang coats on extinguishers or park equipment in front of them.
• Don’t test an extinguisher by squeezing the handle. Even a short burst can let it lose pressure.
• Don’t put a partly used extinguisher back on the wall.
• Don’t use CO₂ in a small, closed space such as a vault without ventilation.

At home

Keep at least one ABC extinguisher on every level of your home, including the kitchen (mounted away from the stove), the garage and the workshop. Learn how to use it before you need it. For a grease fire on the stove, put a lid on the pan and turn off the burner. Never use water. See Preventing Home Fires.

Last updated: October 1, 2026