Even though they are all built for the same basic purpose, all fire extinguishers are not created equal.
There are three primary types of fire extinguishers, each employing a different scientific approach to attack one or more of the three elements of the “fire triangle.” A fire is ignited when these three elements—oxygen, heat, and fuel—are combined.
- Water and Foam fire extinguishers put out fires by removing the heat element, relying on water to douse flames. They also utilize special foam agents to separate oxygen from the other two elements.
- Carbon Dioxide fire extinguishers fight fires by removing the oxygen component of the fire triangle. When the mix of pressurized liquid and gaseous carbon dioxide is released, it effectively smothers the oxygen. These extinguishers also remove heat thanks to a cold-temperature spray.
- Dry Chemical fire extinguishers interrupt the actual chemical reaction that happens within a fire triangle. Using a thin layer of dust, they coat the fuel and separate it from the oxygen in the air.
- “Multipurpose” Dry Chemical versions also feature an agent that serves as a barrier between the oxygen and fuel elements of “ordinary combustible” fires (see Class A fires below).
It’s important to note that all fires are not the same, either. There are three categories of fires. All are unique, and all can be deadly if not contained.
- Class A fires feature what are considered “ordinary combustibles,” such as wood, paper, cloth, and some types of plastic.
- Class B fires consist of flammable liquids like grease and oil, as well as flammable gases.
- Class C fires involve energized electrical equipment.
Be sure to check the label on any fire extinguisher before use, as each type is designed for specific types of fires. Here’s a guide:
Water and Foam extinguishers can only be used on Class A fires. The water stream can potentially spread the flammable liquid in Class B fires, and cause an electrical shock if used on Class C fires.
Carbon Dioxide models are only to be used with Class B and C types of fires. They are generally ineffective against Class A fires because they may not be able to remove enough oxygen to effectively tamp down a fire.
Ordinary Dry Chemical extinguishers only feature powder made for Class B (flammable liquids) and Class C (electrical fires). Therefore, they are typically labeled “BC.”
Only Multipurpose Dry Chemical fire extinguishers can be used on Class A, B, and C fires. Multipurpose dry chemical “ABC” extinguishers will feature a label like this one below to indicate they can be used on all three fire types.
How to Operate Multipurpose Dry Chemical Fire Extinguishers
Because of its effectiveness against so many types of fires, multipurpose dry chemical fire extinguishers are the most widely used. These red, pressurized containers typically weigh between five and 20 pounds and are commonly found in offices, break rooms, labs, and public spaces.
Here are some guidelines on how to safely and effectively use them to put out a fire:
- Hold the extinguisher away from your face and body, and pull the pin. It can be found below the trigger.
- Stand at least 10 feet away from the flames and aim the stream low, at the front edge of the base of the fire. Hold the canister upright and vertically, as it may not function properly in a horizontal or cradled position.
- Squeeze the trigger slowly and spray evenly, sweeping the stream from side to side.
- Only when the portion of the fire closest to you goes out should you move closer to the remaining flames.
Things to Keep in Mind
- Range: A stream from a dry chemical extinguisher will extend between five and 20 feet.
- Time: Typically, a dry chemical extinguisher will discharge for between 10 and 25 seconds.
- Warning: Dry chemical extinguishers could damage electronics. The negative effects may not be immediately evident, as the chemicals used can corrode computers and other equipment slowly over time.
Maintenance
It is advised that building owners or residents inspect their extinguishers every 30 days. This means making sure it is in the appropriate location, easily accessible, and fully pressurized. To check the pressure, consult the gauge on the side of the unit.
These devices also must be properly maintained to ensure they are ready for use in the event of an emergency. Because of the complexity of the parts on fire extinguishers, as well as their importance in terms of keeping occupants and visitors safe, consult with a fire prevention professional to handle regular maintenance checks.
When purchasing new fire extinguishers, always do your research and make sure you have the appropriate type at the ready to fight the fires most likely to occur in your particular work environment, residence, or public space. Not only are they required to meet local, state, and federal regulations, but when combined with carbon monoxide detectors and smoke alarms, these investments could be the difference between suffering minor building damage or something much more serious.
Product Compliance and Suitability
The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.