Not all flames are the same. Thus, you can’t know how to effectively extinguish a fire unless you know which type of blaze you’re facing. There are five main classes of fires that are categorized by what substances fuel their flames.
Class A fire
Also known as “the ordinary” fire, a class A fire involves common flammable solids. Some examples are paper, wood, cloth, rubber, trash, and plastic. Combustible solids are found nearly everywhere. As a result, this class is the most common of the five types of fires.
Despite its ordinary reputation, don’t overlook the danger of a class A blaze. These flames can intensify quickly when there’s enough oxygen and heat to fuel them.
A class A fire can ignite if you leave a candle unattended that catches onto any other flammable solid. It can also occur by a random spark from your fireplace.
Important note: Class A fires aren’t always unintentional. Many people intentionally ignite these flames when they light a match or start a bonfire.
How to put it out
Class A is the easiest type of fire to extinguish. A water agent is the most effective at putting these fires out, and thus, it should be your first choice. However, if you don’t have one on hand, a foam extinguisher can get the job done too.
Most industrial and commercial premises contain a high amount of flammable solids. So, regular site maintenance is critical to keep these blazes to a minimum.
Class B fire
Flammable liquids like gasoline, alcohol, ether, and paint are the culprits of class B fires. As a result, these flames are more common in industries that handle fuels, lubricants, or paint. So, example industries would be warehouses, hospitals, and construction sites.
A Class B blaze is rare, but when it does happen, it’s more deadly than any other class of fire.
Combustible liquids have low flash points. Meaning they burn easily once introduced to an open flame. Certain gases, like propane and butane, can cause a class B flame when a match or lighter ignites the vapors.
How to put it out
The most effective way to extinguish these fires is to use a foam, CO2 gas, or ABC dry powder agent. These are known as class B fire extinguishers because they’re designed to attack flames that spark from flammable liquids.
Remember this! Don’t use a water agent to extinguish a class B fire. This is because heat from gasoline fires will boil water and cause steam burns.
Being aware of the kinds of combustible liquids in your workplace is crucial to reducing the risk of a class B blaze. You should also conduct a COSHH assessment for any hazardous substances. This is a legal requirement that ensures substances are kept in labeled containers and away from ignition sources.
Pro-tip: Invest in fire retardant paint like this Burn Barrier to reduce the risk of a class B fire.
Class C fire
Called the electrical fire class, these flames are most prevalent in facilities that use electrically-powered equipment. Examples of these types of energized equipment include machinery, wiring, controls, and motors.
Electrical failure is the most common way these blazes start. Bad wiring and worn-out breaker boxes can also increase the risk.
How to put it out
You need non-conductive materials to attack an electrical flame. For this reason, it’s very important you don’t use water as a method of putting out these fires. Since water is an electrical conductor, it can exacerbate the flames.
To extinguish a class C fire, you should disconnect the appliance from its power source. Once disconnected, use a carbon dioxide or dry powder fire extinguisher.
Extinguishing an electrical fire can be tricky, so it’s best to follow these prevention tips:
- Never plug-in devices with damaged power cords.
- Don’t cut off the third prong on a power cord.
- Avoid making use of extension cords a regular habit.
- Unplug appliances that produce heat when you’re not using them.
Class D fire
Combustible metals like lithium, titanium, magnesium and aluminum make up class D blazes. These metallic fires aren’t as common as the other classes. But, when they do happen, they often start in laboratories and industrial settings.
Metal shavings and small deposits of flammable metal can cause a class D spark when an open flame is near. Often, alkali metals like aluminum and magnesium can ignite a flame when they’re exposed to water or air.
How to put it out
It can be particularly difficult to extinguish a class D fire. This is due to the fast-growing nature of metallic fires. Plus, they often burn at over 5,000 degrees Fahrenheit.
So, a dry special powder agent is your best bet at tackling these fires. This is because dry agents absorb heat by removing the fuel from oxygen that metal fires need to burn. As a result, they’re able to smother the flames.
You should never use foam and water agents to extinguish these fires. This is because they can cause dangerous explosions; and thus, do more harm than good.
Since these blazes often occur in laboratories, you most likely won’t have to put out a fire in this class in your home. But, regardless of how common a type of fire is, prevention is always important to practice.
If you work in a lab or industrial area with a large volume of metals present, you should follow these prevention tips.
- Conduct regular cleanings to reduce the concentration of metals around your worksite. Removing accumulated metal dust in your facility will mitigate the risk.
- To avoid flammable metal reactions, educate yourself on the properties of the metals in your work setting. Make sure they’re properly contained.
- Certain metals, like phosphorus, are air-reactive. This means they can burst into flames if not sealed to prevent contact with air.
Class K fire
Vegetable oils, fat, grease, and animal oils are the fuel sources of a class K flame. Just like a class B blaze, these flames involve flammable liquids. But, they differ in that they’re all related to cooking. This is why class K fires are most common in the restaurant industry.
Cooking fires are started from the combustion of liquids during food preparation. The primary cause of class K blazes is deep fat frying. Spillages of flammable cooking oils near heat sources come in at a close second.
How to put it out
A water fire can result from pouring water over cooking oil flames. So, the best way to put out an oil fire is to use a wet chemical agent. But, you can also put out an oil/grease fire by smothering it with a fire blanket.
Cooking fires are incredibly dangerous since the flammable oils can splash onto your clothing and skin. Thus, the prevention of these blazes is especially important.
Commercial kitchens should adhere to these fire safety standards.
- While deep fat frying, if you see or smell smoke, you should turn the heat source off immediately. This will prevent the oil from reaching a hazardous temperature.
- Make sure any spilled oil is regularly wiped from surfaces.
- Never leave pans containing oils unattended.
What should you do if you can’t extinguish a fire?
Should you ever find yourself amongst a blaze, your number one priority is your safety. A single flame can transform into a dangerous disaster in under 30 seconds. For this reason, if it’s too difficult to put out a fire, you should immediately evacuate the premises.
Knowing how to extinguish the five classes of fire will prepare you for an unexpected, scary situation. But, always call 911 in the event of a fire to be safe.