Understanding the different types of Fire Extinguishers is very important for our daily Health and Safety. It is equally important for us to know how to use, maintain and handle them in the event of a fire. Fire extinguishers come in different colours, shapes and sizes and each of them is specifically designed to tackle a certain class of fire.

When tackling a fire the first thing to do would be to classify its type. This is because there are several types of fire extinguishers and this guide should help you to identify which class you will need:

Class A = Carbonaceous Fires. These fires involve common combustibles like cardboard, paper, wood and fabrics which turn to ash. They are solid materials and generally produce glowing embers. Class B = Flammable Liquid Fires. All flammable liquids such as Petrol, oil, diesel and kerosene. Class C = Flammable gas fires. These include Butane, Propane. Only attempt to put out this type of fire where there is no risk of explosion. Class D = Metal Fires. For fires involving burning metals like magnesium, Aluminium (you are unlikely to have these in a home or garage setting), these fires are generally unaffected by water or could be dangerous. Class E = Electrical Fires. Electrical fires which usually is the main starting point for a fire due to electrical breakdown or short circuit. Class F = Wet Chemical. A new class specifically for dealing with temperatures greater than 360 degrees and mostly used on chip fat fryers in chip shops or restaurants.

Foam Fire Extinguisher are also known as AFFF foam (aqueous film forming foam) which works together with water to create a film of foam over a fire, which starves the fire of oxygen and therefore preventing re-ignition. By creating this layer of foam over man-made fibres and soft furnishings, it also prevents the items from being liquidated under the intense heat.

Foam extinguishers are safe to use with electrical equipment, but are not recommended for electrical fires, although the electrical equipment will be seriously damaged by the liquid. Water based extinguishers used on electrical fires could cause an electric shock due to water acting as a conductor when in contact with water. Foam fire extinguishers are more expensive than water based ones but are generally more versatile.

The most recognisable protein foam used within the extinguishers is called FFFP, Film Forming Fluoroprotein Foam. This type of protein foam uses naturally occurring proteins instead of synthetic. This type of foam is stiff, heat resistant and extremely durable. Whereas synthetic foams can lower the flash point of certain fuels causing them to become more flammable.

An alcohol-resistant foam fire extinguisher (AR-AFFF) is produced by adding a high molecular polymer to alcohol resistant foam during the manufacturing process. This polymer will then act as a protective membrane between the foam layer and fuel.

Foam fire extinguishers also indicate a drainage rate. This will show how long it will take for 25% of the foam solution to drain from the layer of foam. Therefore a fast drainage time will mean it is very fluid and will spread quickly across the fuel surface of a fire, whereas a slower drainage time mean the foam will move more slowly.

There are 3 types of expansion rate classifications used for foam extinguishers:

Low – less than or equal to 20:1 Medium – between 20:1 an 200:1 High – greater than 200:1

This tells the user how far the foam will expand. So if one cubic metre of foam creates twenty cubic metres of foam when activated this will be labelled as 20:1.

To fill or re-fill your foam fire extinguisher, simply check the foams re-fill drum for the foam concentrate percentage. So for example, 3% foam will be added to 97% water. The lower the concentration of foam, the more cost efficient your extinguisher will be.

Foam fire extinguishers are also identifiable by the writing on a beige label, or green label for Ecofoam. They are suitable on both Class A and B fires, they are non-toxic and will not damage most other materials. They are available in a range of different sizes and are suitable for many different environments.