Even if you are not directly involved in Facility Maintenance activities, you must have come across fire extinguishers at some point and would likely have one or more in your home, office or vehicle.
A fire extinguisher is a hand held, cylindrical shaped device used to extinguish small fires in emergency situations. There are generally 2 types of fire extinguishers: cartridge operated and stored pressure.
Note that these portable fire extinguishers are NOT intended for large out of control fires which endanger or limit the escape of the user or where there is a clear and serious risk of an explosion.
You may have also observed that these fire extinguishers come in different colors and sizes. Be assured that these colorings are not for aesthetics alone. There are actually very important reasons why they are colored differently. In this article we look at what the coloring means and why this knowledge can make the difference between arresting a fire outbreak and aggravating it with disastrous consequences.
Classes of Fire
- Class A Fire
Fire where the fuel is solids such as paper, wood, clothing, plastics and so on. Water works best for this kind of fire.
2. Class B Fire
Flammable or combustible liquids like petrol and kerosene. This kind of fire is extinguished by smothering (cutting off the oxygen supply) using foam extinguishers.
3. Class C Fire
Fire ignited by energized electricity. A non-conductive extinguishing agent such as carbon dioxide is best but only after cutting off power supply to the affected area.
4. Class D Fire
Combustible metal fires. The most common type of metal fire involves Titanium and Magnesium. Dry powder works best for this class of fire by heat absorption and smothering the oxygen supply. Do not use water to attempt fighting metal fires.
5. Class K Fire
Fires involving the various kinds of cooking oil and animal fat and are associated with kitchens. Saponification still remains the quickest and most effective method for fighting kitchen flames. Another option is Purple-K (PKP), a dry chemical fire suppression agent and is known as another very effective extinguishers for kitchen fires.
Color Coding of Fire Extinguishers
- Red: extinguishing medium is water. Absolutely not recommended for electrical and liquid fires as it will aggravate the situation.
- Cream: uses foam. This method was invented by Russian engineer / chemist Aleksandr Loksan in 1902. The components are organic solvents, foam stabilizers, surfactants and corrosion inhibitors.
- Blue: Chemical Powder. Popularly known as the most versatile fire extinguisher. Usually labelled ABC for classes A, B and C fires. The chemical composition differs depending on the class of fire for which it is to be used. This fire extinguisher will leave a residue. It is also not advised to expose yourself to the fumes for extended periods of time
- Black: Carbon Dioxide (CO2). They contain only carbon dioxide gas under high pressure. Ideal for sensitive electrical equipment as it will not leave a residue unlike powder extinguishers.
- Yellow: Wet Chemical Powder. Mostly Suitable for Class A and K fires. The major component is a potassium solution. The mist cools the fire lowering the temperature, then the potassium reacts with the cooking oil in a process known as saponification. The result is a layer of soapy substance over the oil. Not at all recommended for electrical equipment and flammable gases and liquids (petrol etc.)
In 2004, the prevailing fire extinguisher color coding regulation changed to BS EN3. Before then the entire cylinder would be red or black and so on. Now, all cylinders are red but have a colored band to show the class of fire they can be used for. Please refer to the illustration below.
It is important to always note the class of fire before picking up a fire extinguisher. Wrong application of fire extinguishers can lead to severe injuries and even fatalities.