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Ohio State University Extension


Portable Fire Extinguishers

Agricultural Tailgate Safety Training for Operators and Supervisors
Agriculture and Natural Resources
Agricultural Safety and Health Program

Objective: To know how to identify the types of fire extinguishers and be able to properly use them.

Trainer’s Note

All fires are not the same. Know which fire extinguisher units to use for each type of fire. Point out the placement of all units. Have units available for the training session. Discuss how to read the label, select the proper unit, and how to operate, inspect, and maintain it. Let employees practice using an extinguisher. Review the true or false quiz.


Portable fire extinguisher on a tractorFires can occur only in the presence of adequate heat, oxygen, fuel (combustible material), and a chemical reaction, which is the actual fire. Portable fire extinguishers function by releasing an extinguishing agent intended to cool the fuel, remove or displace the oxygen, or stop the chemical reaction. Fire extinguishers can put out or control a fire until help arrives. Use portable units as first-aid or emergency units on small fires or in the initial stages of the fire. The discharge time on most portable units is only seconds, so plan an escape route. Stay low and avoid breathing the smoke and extinguishing agent.

Selecting the Proper Fire Extinguisher

The universal classification system has four designations for fire extinguishers: class A, B, C, and D. Based on the size of a fire to be extinguished and the contained extinguishing agent. Combination extinguishers are suitable for more than one class of fire and are marked with more than one classification letter. The most common multipurpose extinguisher, ABC, is suitable for most instances encountered by a farmer or gardener.

A 20B rating is recommended for non-expert user. Combination extinguishers are suitable for more than one class of fire and are marked as such.

Class Symbol Type of Fuel Aid to Remember
A Green Triangle Ordinary combustibles Things that make Ash
B Red Square Flammable liquids Things that come in Barrels
C Blue Circle Electrical equipment Things with a Charge
D Yellow Star Combustible metals Things that Dent
K Black Square Cooking oils, fats, and grease Things in the Kitchen

The following chart will help classify fires that may occur on the farm.

Location Size Range (lbs) Suggested Placement
Farm shop One unit, (5–10) Near exit door
Combine First unit, (5–10) Near cab door
Second unit, (5–10) On opposite side of cab at ground level
Baler One unit, (2½) On structural member
Car or truck One unit, (2½–5) Accessible to driver
Barn or outbuildings One unit, (5–10) In an accessible location

Reading the Label

The label states the amount of dry or wet chemical contained in the extinguisher. Higher classifications equal greater extinguishing capacity. For example, an extinguisher classified as 4A can extinguish twice as much of a class A fire as an extinguisher classified as 2A. Look for the classification or rating to determine the extinguisher’s capacity.

Operating a Fire Extinguisher

Before you need to use the extinguisher:

  • Examine for defects at time of purchase.
  • Read the operating instructions on the label.
  • Make location of extinguisher known.
Illustration of a person pulling the pin on the fire extinguisher
illustration of fire extinguisher discharging retardant in a sweeping motion at base of fire.

Call for help, as appropriate. Portable fire extinguishers can put out or control a fire until professional help arrives. The discharge time on most portable units is seconds only, so use portable units only on small fires or on fires in their initial stage. Plan an escape route. Stay low and avoid breathing smoke and the extinguishing agent. If the fire starts to spread or continues to burn when the extinguisher is empty, get out!

Remember the PASS acronym when fighting a fire, and follow these steps to operate an extinguisher:

  • Pull the pin.
  • Aim the fire extinguisher nozzle.
  • Squeeze the handle to discharge the fire extinguisher contents. 
  • Sweep the spray back and forth at the base of the fire, not at the flames.

Inspection and Maintenance of a Fire Extinguisher

Inspect units monthly to ensure good working condition and adequate protection. Rotate the fire extinguisher to keep chemical from caking. Have units inspected annually by state certified individual.

Inspection Procedure
  • Are all extinguishers in their recommended location?
  • Is the tamper pin and seal intact?
  • Have all dry chemical fire extinguishers been checked? To check a dry chemical fire extinguisher, remove it from its mounting bracket, invert it, and tap the bottom with a rubber mallet to keep the dry chemical from caking.
  • Does the gauge indicate enough pressure to discharge the contents? If not, replace or recharge the extinguisher as needed.
  • Is the unit damaged?
  • Are the hose and nozzle unobstructed?

Review The Following Points

  • Be prepared. Read the unit label before you need to use it for a fire.
  • Inspect fire extinguishers monthly for proper functioning.
  • Ensure that all designated locations have a fire extinguisher.

About These Modules

The Ag Tailgate Training Series was developed by members of the Agricultural Safety and Health Program in the Department of Food, Agricultural and Biological Engineering. Revised by Dee Jepsen, State Agricultural Safety Leader, with editing assistance by Lisa Pfeifer and Cody McClain.

True or False Answer Key

  1. F
  2. F
  3. F
  4. F
  5. F



Quiz: Portable Fire Extinguishers



True or False?    

1. Fire extinguishers can be used to fight a major fire.    

2. To put out a fire, aim at the fire and spray.    

3. Focus on putting out vertical surface fires.    

4. Any fire extinguisher will put out any fire.    

5. Fire extinguisher should be inspected annually.    


Originally posted Jun 17, 2019.