What are the different classes of fire?

We often get asked what the different classes of fire are. Throughout this article, we will explain what these classes are and what they relate to.

There are different types of fires and each one is put into 6 classes – A, B, C, D, F and electrical, to ensure that the correct fire extinguisher is used. If any of these fires start, it can spread quickly, so it is essential to know which extinguisher to use to be able to put it out in time. Not every fire is the same as different fires can have different hazards and risks. By using the wrong type of fire extinguisher to put out a fire, it could do more harm than good. It can cause damage to buildings or nature, cause injuries and can even take lives, so it is important to know that each fire should be attacked in a different way.

Below, are the 6 classes of fire and what they consist of:

Class A

Class A is a fire involving combustive materials such as wood, plastics, paper, or textiles. This type of fire is one of the most common and it can sometimes be used in controlled circumstances such as a bonfire or other uses in order to provide heat or light. However, when out of control, it is important to try to put it out as soon as possible as the fire can grow and intensify quickly. Class A fires are often more present in jobs like offices, warehouses, manufacturers or even in your homes. To reduce the risk, it is important to have good housekeeping and keep cardboard boxes and paper tidy to avoid the spread of a fire. If you are unsure if your workplace has enforced fire safety measurements, you need to get a qualified engineer in to carry out a fire risk assessment.

Class B

Class B is a fire caused by flammable liquids such as alcohol, petrol, paint, oil etc. These liquids can be highly explosive, so it is important to store them somewhere safe away from sources of ignition and use them sensibly to avoid the risk of starting a fire. In contrast to Class A fires, Class B fires are very rarely controlled and are much more deadly as they produce toxic smoke and fumes. This type of fire can pose a big risk to a lot of industries and can be quite common in places such as petrol stations, factories, schools, offices, and hospitals. Class B fires can ignite by heating them up to extreme temperatures or just with a simple spark, so it is important that you don’t smoke when filling up your car with petrol or diesel for example. You should also always keep any flammable liquids stored away somewhere safe to prevent ignition.

Class C

A Class C fire is the burning of flammable gases such as butane or propane. Butane is often found in items such as cigarette lighters and aerosol sprays, and propane can be used for a whole range of appliances such as a patio heater, a forklift truck, power to an oven or even a BBQ. Both of these gases are heavier than air meaning they will settle to the lowest point, including basements or under houses. If a fire occurs from any gas, it can be highly explosive and difficult to isolate the source and stop its release. They often occur when a leak is present, and the gas has come into contact with an ignition. Making sure that your oven and other gas providers in your home or workplace are installed properly and no pipes or other equipment is damaged, is essential to reducing the risk of Class C fires. If the smell of gas is ever present in your home or workplace, then you should switch off all appliances immediately and get someone to check it out. However, if you have a leak, it is also important not to assume that the gas has gone if there is no smell, as it could still be underground.

Class D

A Class D fire involves flammable metals such as lithium, potassium, aluminium etc. It takes up to a very high temperature for metals to melt however once they ignite is it hard to extinguish as they spread quite quickly. There are some metals that are more fire resistant than others, for example, stainless steel and there are also metals that can catch on fire more easily for example sodium and potassium. Sodium is a highly reactive metal which will immediately burn when it in contact with air or water. This makes this particular metal very hazardous and should be kept away from all sources of ignition. Class D fires are most common in warehouses, factories, and labs, anywhere where metals are usually cut, drilled, or shaved.

Fires caused by electricity

Fires involving electricity are often caused by computers, phones, plug sockets or anything else that involves electricity. The reason this is not classified as a type of fire is that electricity is a hazard to a fire, whereas the other classes mentioned are fuels to a fire. There are 6 most common causes of fires involving electricity which consist of faulty plug sockets and outlets, extension leads, old or faulty appliances, light fixtures and settings, portable heaters, and outdated wiring. Many workers are prone to the risk of these types of fires, including engineers, electricians, office workers and construction workers. There are a lot of things you can do to reduce the risk of fires caused by electricity, the first step being to unplug all appliances when they’re not in use for example phones/heaters. It is also essential to not overload things like extension leads and keep water or any other liquids away from exposed wires, cables, and electrical equipment. As well as this, it is important to get regular PAT testing at your workplace as this will confirm that your appliances are safe and in good working order.

Class F

Class F fires involve combustible cooking oils, fats, or grease which usually pose a threat to restaurants and home kitchens. This is due to the use of deep-fat fryers and chip pans. These types of fires ignite at extremely high temperatures which results in the fire spreading quickly, making it then difficult to extinguish. To avoid a Class F fire, it is essential that you do not leave any hot pans with oil or fat unattended, as this can result in the cause of a fire. As well as this, if any spillages do occur, it is very important that this is cleaned up immediately as this could also result in the event of a fire.

Why is it important to use the correct fire extinguisher on different class fires?

Each class of fire requires certain fire extinguishers to help put it out. It is important that you know which ones are suitable in case of a fire, as using the wrong extinguisher can be life-threatening. But first, you must recognise the type of fire you are facing in order to identify the correct fire extinguisher to use.

The list below shows which fire extinguishers are suitable for different class fires.

Water – Class A

Water Mist – Class A, F and electrical

Dry Powder – Class A, B, C and electrical

Specialist Powder– Class D

Foam – Class A, B and F

CO2 – Class B and electrical

Wet Chemical – Class B and electrical

 

If you are unsure what type of fire extinguisher you need to use in an emergency, you will find a fire extinguisher ID sign above where it is stored. This will tell you the right and wrong types of fires that the extinguisher can be used.