Fire Extinguishers

EH&S Fire Safety manages over 12,000 extinguishers on the University of Wisconsin campus.  Services include:

  • Fire extinguisher annual inspections
  • Fire extinguisher installs & removals
  • Fire extinguisher hands on training
  • Monthly inspections assisted by UW students
  • Plan review for new construction and remodeling projects

If you have questions regarding your fire extinguishers, please contact Fire Safety

Types of Fire Extinguishers

ABC Dry Chemical

ABC Dry Chemical Fire Extinguisher Image

These are found in sizes containing from 5 to 20 pounds of monoammonium phosphate. Monoammonium phosphate is a finely ground extinguishing agent, which looks like yellow talcum powder. Nitrogen gas is used for propellant. This extinguisher is particularly effective on class A, B, and C fires but also extremely messy. Operation is fairly simple. Pull the pin through the seal, aim the extinguisher at the base of the fire, and sweep from side to side. The extinguisher has a range of about 15 feet. These extinguishers are found in hallways and occasionally in labs.

Carbon Dioxide

Carbon Dioxide Fire Extinguisher Image

This is a high pressure vessel filled with either 5 or 10 pounds of liquid CO2. It is only to be used on flammable liquid or electrical fires. Because the CO2 is expelled as a gas the extinguisher has a very limited operation range of about 4 to 6 feet. This extinguisher is found mostly in labs or mechanical rooms. The carbon dioxide extinguisher can be easily identified because it does not have a pressure gauge.


Halon Fire Extinguisher Image

A halon fire extinguisher uses bromochlorodifluoromethane, halon 1211, as its extinguishing agent. Halon is an extremely clean agent that leaves no residue, making it a good agent for use around computers and other sensitive equipment. It has a range of about 15 feet. Pull the pin, aim at the base of the fire, and sweep from side to side. Operation is similar to the ABC extinguisher.

Dry Powder

Dry Powder Fire Extinguisher Image

These extinguishers are for metal fires. Extinguishment is achieved by isolating and smothering the fire with either a copper or sodium chloride based powder. The dry powder extinguishers are mounted on two wheel carts. Operation is similar to ABC, Halon, and Carbon Dioxide extinguishers. Pull pin, take the hose and wand assembly out of the retainer, and aim at base of the fire. It has a range of 3 to 6 feet.

Class K

Class K Fire Extinguisher Image

In recent trends, commercial kitchens have started using more efficient cooking appliances and unsaturated cooking oils that operate at higher temperatures than previous appliances and oils. The Class K extinguisher was developed to combat this new hazard. Class K extinguishers can be found in kitchens on campus or the University Hospital where deep fat fryers are used. This extinguisher uses a wet potassium acetate based, a low pH agent that has a greater firefighting and cooling effect for this type of hazard. Their range is 10-12 feet and will last for about 40 seconds. Once again break the seal, pull the pin, and aim at the base of the fire.

Using a Fire Extinguisher

Before you fight a fire, make sure:

    1. Everyone else is leaving the area, someone has sounded the alarm, and someone has called the fire department.
    2. You have an unobstructed escape route at your back.
    3. The fire is small, confined, and not spreading.
    4. You know what is burning and your extinguisher is right for the fire.
    5. You have been trained to use the extinguisher.

PASS: Fighting a Small Fire

  • Keep your back to a clear exit and stand six to eight feet (two to three meters) away from the fire.
  • To operate your extinguisher, remember the word PASS.

P-PullFire Extinguisher Use Image  

Pull the pin that unlocks the operating lever.        


Aim low. Point the extinguisher nozzle or hose at the base of the fire.


Squeeze the lever above the handle to discharge the extinguishing agent. Release the lever to stop discharge.


Sweep the nozzle or hose from side to side. If the fire is going out, move toward the flames; keep the extinguisher aimed at the base of the fire and sweep back and forth.

  • Watch the fire area once the fire goes out and be prepared to repeat the process if the fire re-ignites.

The Five Classes of Fire

There are five classes of fire. Extinguishers are labeled with standard symbols or letters for the classes of fire they can extinguish.

Class A

Fires that involve ordinary combustible materials such as wood, cloth, paper, rubber, and many plastics.

Class B

Fires that involve flammable liquids, combustible liquids, petroleum greases, tars, oils, oil-based paints, solvent, lacquers, alcohols, and flammable gases.

Class C

Fires that involve energized electrical equipment, such as power tools, wiring, fuse boxes, appliances, TVs, computers, and electrical motors.

Class D

Fires that involve combustible metals such as magnesium, potassium, titanium, zirconium, lithium, and sodium.

Class K

Fires that involve cooking oils, vegetable or animal oils and fats, in commercial cooking equipment.

Fire Extinguisher Training


For fire extinguisher training information, please visit the Fire Safety Training page.