Fire Extinguishing Systems

For your safety and the safety of others at the U-M, it is a good practice to know when to fight a fire, which fire extinguisher to use, and how to put out a fire.  The first decision you MUST make when a fire occurs is to ONLY fight a fire if:

  • The fire is small and contained
  • You are safe from toxic smoke
  • You have a means of escape
  • Your instincts tell you it is OK

If at any time you one of these criteria changes, SOUND THE ALARM and evacuate the area immediately.

Fire Extinguishers

Class A


  • Wood
  • Paper
  • The amount of water the fire extinguisher holds
  • The amount of fire it will extinguish
Class B


Flammable liquids, such as:

  • Grease
  • Gasoline
  • Oil
The approximate number of square feet of a flammable liquid fire that a non-expert person can expect to extinguish NA
Class C


  • Electrical equipment
  • Electrically energized fires
NA The presence of the letter C indicates that the extinguishing agent is non-conductive
Class D Flammable metals (are often specific for the type of metal in question) NA They are NOT given a multi-purpose rating for use on other types of fires
Multi-Class Many extinguishers available today can be used on different types of fires and will be labeled with more than one designator (A-B, B-C, or A-B-C).

Using a Fire Extinguisher

Even though extinguishers come in a number of shapes and sizes, they all operate in a similar manner.  An easy acronym for fire extinguisher use is PASS: Pull, Aim, Squeeze, Sweep.

  1. PULL the pin at the top of the extinguisher that keeps the handle from being accidentally pressed.
  2. AIM the nozzle toward the base of the fire.
  3. Stand approximately 8 feet away from the fire and SQUEEZE the handle to discharge the extinguisher.  If you release the handle, the discharge will stop.
  4. SWEEP the nozzle back and forth at the base of the fire.  After the fire appears to be out, watch carefully since it may re-ignite.

Special Hazards Fire Extinguishing Systems

“Special Hazards” fire extinguishing systems are used in U-M buildings that include:

  • Certain fire hazards that standard automatic sprinklers systems cannot effectively control or extinguish
  • Equipment or operations that upon the application of water may cause excessive collateral damage or an interruption of critical operations

For some of these locations, a special hazards fire extinguishing system may be employed using one of the following fire suppression agents:

  • A non-water, “clean agent”, e.g., a halocarbon (halon) agent or an inert gas agent (a blend of one or more gases of helium, neon, argon, or nitrogen)
  • Carbon dioxide (CO2)
  • Dry chemical
  • Foam

U-M departments that have a special hazard fire extinguishing system installed MUST ensure:

  • The special hazard fire extinguishing system is in proper operating condition
  • That affected building occupants have been provided pertinent health and safety information

For information about special hazards fire extinguishing systems, contact Fire Safety Services at (734) 615-6764.

For more information about the health and safety of the fire suppression agent used in special hazard fire extinguishing system, call EH&S at (734) 647-1142.

Policies, Procedures, and Guidelines

Special Hazards Fire Extinguishing Systems