###### Created: 2025-07-13 17:46 ###### Areas & Topics: # ###### Note Type: #permanent ###### Connected to: [[]] - There are lots of different types of fire extinguishers developed for different use cases. - In order to know how best to use them, you need to know about the main types of fire and the main types of extinguishers. - In the UK, there are 5 main types of extinguisher you are likely to come across and 6 general classes of fire. ### Fire Classes - Class A – combustible materials caused by flammable solids such as wood, paper, and fabric - Class B – flammable liquids such as petrol, turpentine or paint - Class C - flammable gases: like hydrogen, butane or methane - Class D fires - combustible metals, including chemicals such as magnesium, aluminium or potassium - Electrical fires - electrical equipment: once the electrical item is removed, the fire changes class - Class F fires - cooking oils and fats (typically a chip pan fire). ### Extinguisher Classes Water - Suitable for fires involving solid materials (class A) - Isn't used for other types of fire because it's ineffective against gases, acts as an electrical conductor so shouldn't be used on electric fires and water can splash oils and similar substances around which can spread those type of fires. Foam - Suitable for flammable liquids but can be used on all non-electrical fires (class A and B). - The foam is mainly water-based, and when used forms a film over the top of fires to help smother them (which is why its best for class A and B). - The foam ineffective against gases however, and can splash oil and similar substances which is why it isn't used in other types of fire. Carbon Dioxide (CO2) - Suitable for flammable liquids and electrical fires. (Class B and Electrical). - The extinguisher produces a jet of pure CO2, which initially displaces oxygen to starve fires. - Since CO2 doesn't conduct electricity or corrode electrical equipment, this makes it suitable for electrical fires and with flammable liquids. - However, because it doesn't have a cooling effect it can't be used on flammable solids (Class A) and the high-pressure jet can blast other gases and oil-based fires and spread them, making it unsuitable for this as well. - Its displacement of oxygen makes CO2 in this form an aspyhixiant gas, meaning it shouldn't be used in confined spaces as there is a risk of suffocation (due to lack of oxygen). Dry Powder - Suitable for all types of fire except cooking oils and fat. - The powder forms a barrier between a fuel source and the fire, thereby smothering it. - Ideally however, dry powder should not be used on sensitive electrical equipment such as computers as the powder corrodes electrical equipment. Wet Chemical - Suitable specifically for deep fat cooking fires i.e. in kitchens and food-processing plants (Class F only). - They contain potassium salts, which are sprayed in a fine mist (to prevent spreading oil and flames) and react with the oil via saponification, creating a soapy film that smothers the fire. - Unless specialised however, they shouldn't really be used for other types of fire. ### Which fire extinguisher can be used on each type of fire? | **Type** | **Class A** | **Class B** | **Class C** | **Class D** | **Electrical** | **Class F** | | ---------------- | ----------- | ----------- | ----------- | ----------- | -------------- | ----------- | | **Water** | Yes | No | No | No | No | No | | **Foam** | Yes | Yes | No | No | No | No | | **CO2** | No | Yes | No | No | Yes | No | | **Dry powder** | Yes | Yes | Yes | Yes | Yes | No | | **Wet chemical** | Yes | No | No | No | No | Yes | ### Sources Fire Protection Association - https://www.thefpa.co.uk/advice-and-guidance/advice-and-guidance-articles/what-fire-extinguisher-to-use- Fire Safety Equipment Foam Extinguishers- https://www.firesafetyequipment.co.uk/help-and-advice/what-are-foam-fire-extinguishers-used-for/ Surrey Fire and Safety Ltd Wet Chemical Extinguishers. - https://surreyfire.co.uk/wet-chemical-fire-extinguishers/ Surrey Fire and Safety Ltd Dry Powder Extinguishers - https://surreyfire.co.uk/dry-powder-fire-extinguishers/ Surrey Fire and Safety Ltd CO2 Extinguishers - https://surreyfire.co.uk/co2-fire-extinguishers/