Fire Classes A, B, C, D and F Explained Simply
Fire classes A, B, C, D and F describe the type of material that is burning. These classes are shown on fire extinguishers and help with selecting a suitable extinguishing agent. Anyone who chooses an appliance solely by its colour overlooks the decisive information: the letters and extinguishing rating on the label. Training services for organisations connect these fundamentals with safe behaviour in the event of a fire.
Why fire classes matter
Electricity is not a separate fire class. For electrical installations, observe the suitability information, voltage limits and minimum distances stated on the fire extinguisher.
An extinguishing agent may be effective on one fire but unsuitable or dangerous on another. Fire classes provide a consistent classification. Pictograms and letters on the fire extinguisher show the groups of materials for which the appliance has been tested.
ASR A2.2 requires sufficient extinguishing capability for every fire class present at the workplace. For classes A and B, the extinguishing rating is additionally converted into extinguishing units. For classes C and D, suitability is stated without a numerical rating. For class F, the number indicates the volume of cooking oil or fat extinguished under test conditions.
Fire class A: solid materials that form embers
Class A covers solid materials that normally burn while forming glowing embers. Typical examples include wood, paper, cardboard, textiles and many plastics. This fire class is particularly common in offices, schools, warehouses and administrative premises.
Water and foam may be effective through cooling, provided there are no electrical or material-specific hazards. The class A marking and stated extinguishing rating, such as 21A, are decisive.
Fire class B: liquids and materials that become liquid
Class B covers flammable liquids and materials that become liquid when heated. Examples can include petrol, paints, solvents, alcohol, wax and certain plastics. The extinguishing agent should interrupt combustion or separate the surface from oxygen.
Suitable foam, dry powder or CO₂ extinguishers may be used depending on the substance and surroundings. A jet of water can spread a burning liquid and enlarge the fire. The class B suitability must therefore be checked on the appliance.
Fire class C: flammable gases
Class C covers gases such as propane, butane, methane and acetylene. Extinguishing a gas flame can be dangerous if unburnt gas continues to escape and forms an explosive mixture.
Safely stopping the gas supply is therefore of central importance. Extinguishing measures require a professionally designed procedure and must not place anyone at risk. Appliances suitable for class C fires carry the letter C.
Fire class D: metals
Burning metals such as magnesium, finely divided aluminium, sodium or lithium can reach extremely high temperatures and react violently with unsuitable extinguishing agents. Standard water, foam, CO₂ and ABC dry powder extinguishers are not automatically suitable.
Metal-fire extinguishers use special powders and a particular application method. Organisations with a metal-fire hazard need a specific risk assessment, suitable equipment and dedicated instruction.
Fire class F: cooking oils and fats
Class F covers cooking oils and fats in fryers and cooking appliances. Their high temperatures make these fires particularly dangerous. Water can vaporise suddenly and explosively eject burning fat from the container.
Suitable wet-chemical extinguishers carry the class F marking. The number before the F, such as 25F or 75F, refers to the volume extinguished under test conditions. Kitchens also need clear shut-down and alarm procedures.
How to use fire classes in the workplace
Record the combustible materials in each area and compare them with the markings on the fire extinguishers. Then assess extinguishing ratings, quantities, locations and special risks. An appliance marked with several letters is suitable only if the consequential damage and risks to people are also acceptable.
Fire safety assistants should not have to identify the fire class for the first time during an emergency. Site-specific instruction covers typical materials, appliance locations and clear limits. If there is smoke, rapid fire spread or an unclear situation, withdrawal takes priority. Practical fire safety assistant training in Munich makes labels, extinguishing effects and equipment limits directly tangible.
Frequently asked questions
Which fire class applies to electrical equipment?
Electricity is not a separate fire class. The material that is burning is decisive. The electrical suitability, maximum voltage and minimum distances stated on the extinguisher must also be observed.
Why is there no fire class E?
The former classification of electrical fires as a separate class is no longer used. Fire extinguishers instead carry specific information on safe use around electrical installations.
Which fire class applies to a lithium-ion battery?
This cannot be answered universally with a single letter. Design, state of charge and materials contained in the battery affect how the fire develops. A specific risk assessment and suitable protection concept are required.
Sources and technical basis
Learn fire classes in practice, not only in theory
Identify the correct extinguishing agent
Fire safety assistant training explains labels, extinguishing effects and safe limits using workplace examples.
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