Portable Fire Extinguishers

There were an estimated 1.6 million fires in 2007 according to the National Center for Health Statistics Mortality Data, Tennessee is ranked 5th in the United States in fire death rates. Portable fire extinguishers are intended to be used as a first line of defense to cope with small fires. When used properly, fire extinguishers can save lives and property by putting out a small fire or by controlling a fire until additional help arrives.

Fight or Flight?

When a fire occurs the decision whether or not you should fight the fire with a portable fire extinguisher or to simply evacuate must be made. Most small fires can be put out quickly by a well-trained person with a portable fire extinguisher. However, the person voluntarily willing to put out a small fire must understand how to properly use a fire extinguisher and the hazards involved.

Should you evacuate or be prepared to fight a small fire?

Portable fire extinguishers can save lives and property if used properly. ETSU recommends that before attempting to extinguish a fire that you not only complete this written training, but also complete the hands-on training provided by our Fire Protection Manager (439-7785).

Risk assessment

Portable fire extinguishers have two functions: to control or extinguish small or incipient stage fires and to protect evacuation routes that a fire may block directly or indirectly with smoke or burning/smoldering materials.

To extinguish a fire with a portable extinguisher, a person must have immediate access to the extinguisher, know how to actuate the unit, and know how to apply the agent effectively. Attempting to extinguish even a small fire carries some risk. Fires can increase in size and intensity in seconds, blocking the exit path of the fire fighter as well as create a hazardous atmosphere. In addition, portable fire extinguishers contain a limited amount of extinguishing agent and can be discharged in a matter of seconds. Therefore, individuals should attempt to fight only very small or incipient stage fires.

Prior to fighting any fire with a portable fire extinguisher you must perform a risk assessment that evaluates the fire size, the fire fighters evacuation path, and the atmosphere in the vicinity of the fire.

Risk Assessment Question Characteristics of incipient stage fires or fires that can be extinguished with portable fire extinguishers Characteristics of fires that SHOULD NOT be fought with a portable fire extinguisher (beyond incipient stage) - evacuate immediately
Is the fire too big? The fire is limited to the original material ignited, it is contained (such as in a waste basket) and has not spread to other materials. The flames are no higher than the firefighter's head. The fire involves flammable solvents, has spread over more than 60 square feet, is partially hidden behind a wall or ceiling, or cannot be reached from a standing position.
Is the air safe to breathe? The fire has not depleted the oxygen in the room and is producing only small quantities of toxic gases. No respiratory protection equipment is required. Due to smoke and products of combustion, the fire cannot be fought without respiratory protection.
Is the environment too hot or smoky? Heat is being generated, but the room temperature is only slightly increased. Smoke may be accumulating on the ceiling, but visibility is good. No special personal protective equipment is required. The radiated heat is easily felt on exposed skin making it difficult to approach within 10-15 feet of the fire (or the effective range of the extinguisher). One must crawl on the floor due to heat or smoke. Smoke is quickly filling the room, decreasing visibility.
Is there a safe evacuation path? There is a clear evacuation path that is behind you as you fight the fire. The fire is not contained, and fire, heat, or smoke may block the evacuation path.

Fire and extinguisher operation

Fire triangle

To understand how fire extinguishers work, you need to understand a little about fire. Fire is a very rapid chemical reaction between oxygen and a combustible material, which results in the release of heat, light, flames, and smoke.

For fire to exist, the following four elements must be present at the same time:

  • Enough oxygen to sustain combustion,
  • Enough heat to raise the material to its ignition temperature,
  • Some sort of fuelor combustible material, and
  • The chemical reaction that sustains fire

How a fire extinguisher works

Portable fire extinguishers apply an extinguishing agent that will either cool the burning fuel, displace or remove oxygen, or stop the chemical reaction so a fire cannot continue to burn. When the handle of an extinguisher is compressed, agent is expelled out the nozzle. A fire extinguisher works much like a can of hair spray.


All portable fire extinguishers must be approved by a nationally recognized testing laboratory to verify compliance with applicable standards. Equipment that passes the laboratory's tests are labeled and given an alpha-numeric classification based on the type and size of fire it will extinguish.

Let's take a look at the label pictured. The classification is: 1-A:10-BC


The letters (A, B, and C) represent the type(s) of fire for which the extinguisher has been approved.

Fire/Fuel Types

  • CLASS A - Ordinary combustables such as wood, paper, plastics, rubber, etc
  • CLASS B - flammable or combustible liquids
  • Class C - Anything inolving electronics
  • Class D - Flammable Metals

The number in front of the A rating indicates how much water the extinguisher is equal to and represents 1.25 gallons of water for every unit of one. For example, a 4-A rated extinguisher would be equal to five (4 x 1.25) gallons of water.

The number in front of the B rating represents the area in square feet of a class B fire that a non-expert user should be able to extinguish. Using the above example, a non-expert user should be able to put out a flammable liquid fire that is as large as 10 square feet.

Types of fire extinguishers

ETSU mainly uses these type of fire extinguishers. They are CO2, dry chemical, clean guard.

Extinguisher Type

Type of Fire


Flammable Liquids

Fires in oils, gasoline, some paints, lacquers, grease, solvents, and other flammable liquids require an extinguisher labeled B.

Discharge is 3-8 feet and lasts from 8-30 seconds. There are no gauges and are weighed to determine how much agent is left.

Electrical Equipment

Fires in wiring, fuse boxes, energized electrical equipment, computers, and other electrical sources require an extinguisher labeled C.

Discharge is 5-20 feet and lasts from 8-25 seconds.

Ordinary Combustibles, Flammable Liquids, or Electrical Equipment

Multi-purpose dry chemical is suitable for use on class A, B, and C.


Puts out electronic fires only.
Replaces Halon 1211 for application where the agent must be clean and electronically non-conductive, such as computer and telecommunication rooms.

Class K

Kitchen Fires

Fires involving combustible cooking fluids such as oils and fats.



  • Never use water to extinguish flammable liquid fires. Water is extremely ineffective at extinguishing this type of fire and may make matters worse by spreading the fire.
  • Never use water to extinguish an electrical fire. Water is a good conductor and may lead to electrocution if used to extinguish an electrical fire. Electrical equipment must be unplugged and/or de-energized before using a water extinguisher on an electrical fire.

Fire Extinguiser Use

Using a fire extinguisher


The following steps should be followed when responding to an incipient stage fire:

  • Everyone is leaving or has a left the building.
  • Pull the fire alarm and call 911 or 9-4480.
  • Identify a safe evacuation path before approaching the fire. Do not allow the fire, heat, or smoke to come between you and your evacuation path.
  • Select the appropriate type of fire extinguisher.
  • Discharge the extinguisher within its effective range using the P.A.S.S. technique (Pull, Aim, Squeeze, and Sweep).
  • Make sure you have a safe way out and can fight the fire with your back to the exit.
  • Evacuate immediately if the extinguisher is empty and the fire is not out.
  • Evacuate immediately and close the door if the fire progresses beyond the incipient stage.

Most fire extinguishers operate using the following P.A.S.S technique: FireExt

  • PULL... Pull the pin. This will also break the tamper seal.
  • AIM... Aim low, pointing the extinguisher nozzle (or its horn or hose) at the base of the fire.

    Note: Do not touch the plastic discharge horn on CO2 extinguishers, it gets very cold and may damage skin.

  • SQUEEZE... Squeeze the handle to release the extinguishing agent.
  • SWEEP... Sweep from side to side at the base of the fire until it appears to be out. Watch the area. If the fire re-ignites, repeat steps 2 - 4.

    If you have the slightest doubt about your ability to fight a fire....EVACUATE IMMEDIATELY!

Extinguisher Placement and Spacing


Portable fire extinguishers at ETSU typically can be found: 1) In the corridors of academic and office buildings; 2) In or immediately outside all laboratories where chemicals are stored and used; 3) In or immediately outside mechanical spaces where motorized or other equipment is present which may reasonably cause a fire; 4) In campus storage buildings, and/or mounted inside certain university vehicles.

To avoid putting people in danger, fire extinguishers are strategically located throughout the University and readily accessible in the event of a fire.

OSHA Requirements


An employer must:

  • Provide an educational program to familiarize employees with the general principles of fire extinguisher use and the hazards involved with incipient stage fire fighting. Provide this education at least annually.
  • Inspect, maintain, and test all portable fire extinguishers.