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How Does A Fire Extinguisher Work?

By September 17, 2021September 20th, 2021Automobile, Boat, Condo, Home


­Fires result from a chemical combustion reaction, usually between oxygen and some fuel, such as gasoline or wood. Of course, these fuels do not catch on fire independently but must be heated to their ignition temperature.

Once all the elements are in place, the fire can be pleasurable, as when it is in a fireplace while you sit in front of it with a loved one, or it can be terrifying and dangerous when it is burning out of control. If that fire happens to start in your home, a fire extinguisher could save your property and perhaps your life.


What is inside a fire extinguisher?

On the inside, a fire extinguisher resembles an oversized aerosol can containing two different substances: one of them—a solid, liquid, or gas–is in there to fight the fire, while the other is a pressurized propellant that helps to “propel” the substance toward the fire. The fire-fighting substance often identifies fire extinguishers.


How does a fire extinguisher work?

­Here is a sequence of events for a simple wood fire:

Things like friction, sparks, the sun, or certain chemicals heat the wood to a high temperature. After the wood reaches about 500 degrees Fahrenheit, the heat begins to decompose the cellulose material that makes up the wood. That decomposed material is released as volatile gases, usually a compound of hydrogen, carbon, and oxygen.

The gases rise through the air, making a flame that produces light and heat. The heat from the flame keeps the fuel at the ignition temperature, and it will burn as long as there is fuel and oxygen. Notice that the three essential elements for a fire, mentioned earlier, are present in this example: fuel, high heat, and oxygen.

­­Fire extinguishers remove at least one of these elements so that the fire will die out. They do it in  two primary ways: putting water on the fire to cool it below the ignition temperature, or smothering it so that it cannot get oxygen. (Another way to stop a fire is to remove the fuel, but this is usually extremely difficult. For instance, if a house is burning, its material is the fuel and will not be gone until the fire has used it up).

Fire extinguishers are thick-walled metal cylinders filled with either water or a smothering material. Depressing an operating lever at the top of the cylinder forces out the cylinder’s material under high pressure. To use an extinguisher correctly, direct the stream toward the fuel instead of the flame, and move the spray with a sweeping motion.


What comes out of a fire extinguisher?

Their fire-fighting substance classifies many fire extinguishers. There are four primary types:

  1. Water extinguishers are the most common type and are cylinders filled with mostly water and nitrogen or carbon dioxide as a propellant. These extinguishers effectively remove the heat from the fire and help to smother it.
  2. Dry powder extinguishers contain a powdered mixture that absorbs heat while melting and coating the fuel. The powder blocks the fire’s oxygen supply and prevents it from making flammable vapors. Monoammonium phosphate is the most commonly used powder. Other extinguishers may contain sodium bicarbonate (baking soda) or potassium bicarbonate.
  3. Foam extinguishers are filled with water and foam, while compressed nitrogen is the propellant. Foam smothers the fire by cutting off its oxygen, but it also serves to absorb heat since it contains plenty of water.
  4. Carbon dioxide (CO2) extinguishers are made up of a mixture of liquid and gaseous carbon dioxide. Carbon dioxide, usually a gas at room temperature and pressure, becomes a liquid under pressure. Releasing the pressure causes the gas to expand, creating an enormous white jet. CO2 both smothers the oxygen and, as it turns back into a gas, pulls a substantial amount of heat from the fire.


What do ABC fire extinguishers work for?

Five types of extinguishers are classified by the material for which they are intended:

  • A: Green: Ordinary combustibles such as wood, cloth, and paper.
  • B: Red: Flammable liquids such as grease, oil, solvents, and paint.
  • C: Blue: Live electrical equipment including motors, wiring, and electrical panels.
  • D: Orange: Combustible metals like magnesium.
  • K: Black: Cooking oils, vegetable oils, and animal fats.

Be sure to use the right extinguisher for the fire, or you could make the fire worse and put yourself in danger. If you are in doubt, get to safety and call the fire department.


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