This lesson is theory only: it explains extinguishers so that a marshal can check and understand them. It does not teach you to use one. Practical training is your employer's part, given by a competent person.
Marshals do not have to fight fires
An extinguisher on the wall does not mean every marshal is expected to use it. Your employer decides who, if anyone, is trained to use equipment (Fire Safety Order, article 13). Many workplaces say plainly: raise the alarm and leave. If you have not been trained, do not use one.
Fire classes
The class depends on what is burning (BS EN 2):
- Class A: ordinary solids, such as wood, paper, cardboard, fabric.
- Class B: flammable liquids, such as petrol, diesel, paint and solvents.
- Class C: flammable gases, such as propane, butane and methane.
- Class D: metals, such as magnesium and lithium metal.
- Class F: cooking oils and fats, such as in a deep-fat fryer.
- Electrical: there is no letter class, but fires started by or near live equipment need extinguishers that are safe on electricity. Once the power is off, the fire is another class.
Extinguisher types and colours
In the UK, the body of an extinguisher is red. A colour band or panel shows what it contains (BS EN 3 and BS 7863). Always read the label too.
- Water: red with no band, or a plain red label. For Class A. Never on electrical equipment, burning oil or burning liquids. Water spreads oil fires and conducts electricity.
- Foam: cream. For Class A and B. Not for live electrical equipment unless the label says it is safe.
- Dry powder: blue. For Class A, B and C, and often electrical. It does not cool, so a fire can restart, and the cloud of powder makes it hard to see and breathe indoors.
- Carbon dioxide (CO2): black. For Class B and electrical. It leaves no residue; the horn becomes extremely cold, and in small closed rooms the gas can affect breathing.
- Wet chemical: yellow. For Class F cooking oil and fat fires, and also useful on Class A.
- Water mist: usually white. Suitable for several classes, including some electrical fires, as the label says.
- Class D powder: for metal fires only, in places where such metals are used.
- Halon: banned. An old extinguisher with a green band should be reported and replaced.
Fire blankets
A fire blanket smothers a small fire in a pan or on clothing. Like an extinguisher, it is for people who have been shown how to use it. A marshal checks that it is in place and not blocked.
Where extinguishers go
The responsible person decides the type and number from the fire risk assessment, often using BS 5306-8. Extinguishers are usually on escape routes, near exits and near the hazard, easy to reach and signed, and of the right type for the risks nearby: for example CO2 near electrical equipment and wet chemical in a kitchen.
What a marshal checks
- Present and in place: not moved, hidden or used as a door stop.
- Pin and tamper seal in place; no sign of use.
- No damage: dents, corrosion, cracked hose, blocked nozzle.
- Gauge (if fitted) in the green zone.
- Service tag in date: extinguishers are usually serviced once a year by a competent person (BS 5306-3).
- Signs present and visible.
Report faults to the named person. Do not recharge, repair or move an extinguisher unless told to.
If an extinguisher is ever to be used
Only your employer's practical training prepares you for this. The usual conditions are:
- the alarm is raised first and 999 called;
- the fire is small and has only just started;
- the person is trained and has the right type of extinguisher;
- they have a clear escape route behind them;
- they stop and leave if the fire grows, if there is smoke or if the extinguisher runs out.
Never use water on burning oil or fat, and never carry a burning pan.
Special risks
- Lithium-ion batteries (e-bikes, scooters, power tools, vapes) can burn violently, give off toxic smoke and reignite. Do not fight a battery fire: leave, close the door and call 999.
- Gas cylinders near a fire may explode. Tell the fire and rescue service where they are.
Key points
- Class A solids, B liquids, C gases, D metals, F cooking oils; electrical needs care.
- Colour bands: cream foam, blue powder, black CO2, yellow wet chemical, usually white water mist.
- Plain water must never be used on electrical or oil fires.
- Marshals check extinguishers are present, sealed, undamaged and in date.
- Using one needs practical training. If you are not trained, leave.