Types of Fires and How They Are Extinguished

4/25/2018 (Permalink)

Knowing the type of fire you are trying to extinguish is essential for safely attempting to put it out and can help avoid making the fire worse.

According to the U.S. Fire Administration, there were approximately 1,345,500 fires nationwide in 2015. As a homeowner or property manager, being aware of the different types of fires and how they are extinguished can help you to quickly resolve a fire incident, avoid making it worse, and even determine when the risks are too high for any attempt at extinguishing the flames. In the event of any fire, your safety and health should be your number one priority at all times. If you are concerned about your safety at any point, vacate the property, keep a safe distance, and wait for your local fire department to arrive. The types of fires are generally split into the 5 classes listed below.

Class A - Ordinary Combustible Fires

This common type of fire happens when materials are heated to their ignition temperature. Heat, oxygen, and fuel will allow a combustible fire to continue burning. Rubber, plastic, textiles, wood, paper and organic carbon-based compounds are a few of the materials that can be involved in these types of fires.

Combustible fires are usually the most simple to extinguish since spraying with water will cool the flames and source material. By removing the supply of heat, the fire is left without the essentials needed to burn. A water-based or foam based fire extinguish is recommended for Class A fires.

Class B - Flammable Liquids

Any liquid substance that has an ignition temperature below 100°C is classified as a flammable liquid. These liquids burn easily due to having a low flashpoint ( the temperature of a substance where enough vapor to be ignited is released). If a spark, flame, or any other source of ignition is applied to a flammable liquid, they can burn at any temperature. Types of flammable liquids include, but are not limited to, petrol, kerosene, alcohol, solvents, and paints.

When attempting to extinguish a Class B fire, it is important that you DO NOT use water to put the fire out. Splashing water can cause the flammable liquid to spread, spreading the fire along with it. Instead, smother the flames using a foam extinguisher. It is also important to note that Class B fires produce a thick and black toxic smoke, so avoiding the fire and waiting for the professionals may be the best route.

Class C - Flammable Gases

Butane, propane, and petroleum are a few flammable gases that have the potential for creating explosions if triggered by a spark. These fires are amongst the most dangerous and only need about a 5% concentration of flammable gas in the air to burn.
These fires should always be left to your fire department. Once on scene, they will have to isolate the fire’s gas supply and then use dry powder extinguishers. Most other extinguishers are ineffective against Class C Fires.

Class D - Metal Fires

Metals are good conductors and most require a lot of heat to ignite. Certain types of metals can burn if ignited. Metal shavings and powders pose a higher fire risk than solid masses of metal. Alkali metals such as potassium, magnesium, and sodium can burn when in contact with air and water. Therefore, spraying water or foam onto metal fires will increase the intensity of the flames and can potentially cause explosive reactions sending pieces of burning metal in all directions.

When dealing with a Class D fire, the safest approach is usually to allow the fire to burn out on its own. These type of fires tend to occur in industrial properties with large amounts of burning metal and an increased chance of explosions. Class D fires have a tendency for producing large amounts of ash, which builds up and starves the fire’s supply of oxygen. For metal fires that are spotted early, special type D powder fire extinguishers can be effective. Just make sure to check that they are the specific dry powder type intended for use on metal fires.

Electrical Fires

Electrical fires do not have a class of their own and are designated to Class C in the United States. However, they have their own fire safety requirements and are important to mention. These fires can be caused by short circuits, overloaded switchboards, faulty equipment and damaged wiring.

Before attempting to extinguish an electrical fire, it is important to isolate its electrical supply as quickly as possible. Water and foam are both conductors for electricity, so even after isolation, it is not safe to use them as extinguishers. The only types of extinguishers recommended for safely addressing electrical fires are carbon dioxide and dry powder fire extinguishers.

Class F - Cooking Oil Fires

Fires that involve cooking oil and fats are classified as Class F. These fires are common in homes, businesses and professional kitchens. They pose a very difficult challenge to extinguish, due to the high temperatures involved. Simply trying to cool the fire with water will not work. In fact, using water on a burning pan is likely to cause a rapid spreading out of the flames, making the fire worse and potentially injuring anyone in its vicinity.

For this reason, special fire extinguishers have been developed to address Class F fires. Wet chemical extinguishers contain a formula which cools the fire and then mixes with the oil to seal the surface and prevent re-ignition.

Fire Damage Restoration

SERVPRO of Winter Park does not extinguish fires. In case of a fire emergency, please contact your local emergency services and fire department for assistance. If you have suffered from fire damage to your property, give us a call at 407-678-5391. Our phone lines are open 24 hours to assist you and our skilled technicians can help you assess the extent of the damage to get the fire damage restoration process going.