The Classes of Fire and Which Extinguisher to Use
Not every fire is the same, and grabbing the wrong extinguisher can make a small fire far more dangerous. This guide walks through every class of fire you might meet in an Irish workplace and the extinguisher — and colour code — that goes with each.
Most of us think of fire as a single thing, but a chip pan blaze, a burning laptop charger and a flaming tin of solvent each behave very differently and need different agents to put them out safely. That is why fires are sorted into classes — a shorthand that tells you what is actually burning and which extinguisher will smother it rather than spread it.
Why fires are classified at all
The classification system exists because the way you stop a fire depends on its fuel. Cooling works on burning wood but is useless — even hazardous — on a live electrical fault, and aiming a jet of water at burning oil can throw flaming droplets across the room. Matching the agent to the fuel is the whole point, and the classes give everyone a common language to do it.
The right extinguisher in trained hands stops a small fire in seconds. The wrong one can turn a manageable flame into a serious emergency.
The classes of fire
Class A — solid combustibles
These are everyday solids: paper, cardboard, wood, textiles, furniture and most plastics — by far the most common office and warehouse fires. Class A fires leave glowing embers and need to be cooled right through, so water and foam extinguishers handle them well.
Class B — flammable liquids
Petrol, diesel, paint, solvents, white spirit and many cleaning products fall here. Liquid fires spread fast and reignite easily, so they need to be smothered to cut off oxygen. Foam, dry powder and carbon dioxide are the usual answers. Never use water on a Class B fire — it can scatter the burning liquid.
Class C — flammable gases
Class C covers gases such as butane, propane, methane and natural gas. The most important action is rarely the extinguisher at all — it is isolating the supply. Putting out the flame while gas keeps escaping risks a build-up and explosion, so shutting off the source comes first; where safe, dry powder can then knock down the flame.
Class D — metals
Burning metals such as magnesium, aluminium swarf, sodium and lithium are rare outside engineering and certain manufacturing settings, but extremely dangerous: they burn ferociously and react violently with water. Class D fires require specialist dry powder agents formulated for the specific metal — standard extinguishers will not do.
Electrical fires
Electrical fires are not given a letter of their own, because electricity is the ignition source rather than the fuel — think faulty chargers, overloaded sockets and machinery. The golden rule is a non-conductive agent: carbon dioxide is ideal, and dry powder can also be used. Water and foam must be kept well away from live equipment to avoid electric shock.
Class F — cooking oils and fats
Class F is the kitchen fire — deep-fat fryers, chip pans and hot cooking oils that ignite at very high temperatures. These fires are notoriously stubborn and dangerous; throwing water on them causes a violent steam explosion. The answer is a wet chemical extinguisher, which cools the oil and forms a soapy seal over the surface to stop reignition.
Key takeaways
- Class A — solids (paper, wood, fabric): cool with water or foam.
- Class B — flammable liquids: smother with foam, powder or CO₂; never water.
- Class C — flammable gases: isolate the supply first, then dry powder if safe.
- Class D — burning metals: specialist metal-rated dry powder only.
- Electrical — not a class: use CO₂ or dry powder, keep water and foam away.
- Class F — cooking oils and fats: wet chemical extinguisher only.
Matching extinguishers to classes — and the colour codes
Extinguishers in Ireland are red, with a coloured band or label that tells you the type at a glance. Learning the bands makes the right choice instant:
- Water — red label. Class A only. Simple, effective on solids, never for liquids or electrics.
- Foam — cream label. Classes A and B. A versatile all-rounder for offices and stores.
- Dry powder — blue label. Classes A, B and C, and safe on electrical equipment. Powerful but messy, so it is often kept for plant rooms, garages and outdoors.
- Carbon dioxide (CO₂) — black label. Class B and electrical fires. Leaves no residue, making it the favourite for server rooms and around computers.
- Wet chemical — yellow label. Class F (and some Class A). The kitchen extinguisher for fryers and cooking oils.
- Specialist powder — blue label, metal-rated. Class D only, chosen for the specific metal present.
The practical lesson is to provide the right mix for each area: a kitchen needs wet chemical, a server room needs CO₂, and a general office is usually well served by foam plus a CO₂ for electrics. Getting this right is part of an employer's duty under the Fire Services Acts 1981 and 2003 and the Safety, Health and Welfare at Work Act 2005, supported by guidance from the Health and Safety Authority (HSA) and your local fire authority. Provision is only half the job, though — an extinguisher is only useful if people nearby can choose correctly in the few seconds that matter, and that confidence comes from training.
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Putting it into practice
You can now read any room for fire risk: solids are Class A, the cleaning cupboard holds Class B liquids, the kitchen brings Class F, and every socket and charger is an electrical risk. Pair each risk with the correct extinguisher type and colour, keep units serviced and unobstructed, and make sure staff have practised the choice — and a small fire stays small. For the next step, learn the safe technique in our guide on how to use a fire extinguisher, and see how it fits your wider obligations in fire safety in the workplace in Ireland.
