Welcome to Part 4 of our 14-day fire and security series.
Choosing the correct extinguisher starts with identifying the materials that could burn. Different fires require different extinguishing agents. Using the wrong type can spread the fire, create an electric shock risk or cause serious injury.
This guide explains common UK fire classes and the main fire extinguisher types used in homes, workplaces and commercial premises. It also covers inspection, servicing, signage, access and staff training.
Always follow the current UK guidance and the instructions printed on the extinguisher label. Fire extinguishers are only suitable for a small, contained fire where you have been trained and have a clear escape route.
Fire safety comes first
Before considering an extinguisher:
- Raise the alarm.
- Call 999.
- Evacuate the building.
- Close doors behind you if it is safe.
- Do not re-enter.
- Only use an extinguisher if you are trained, the fire is small and your escape route remains clear.
Never put yourself at risk to protect property. A fire can grow rapidly, produce toxic smoke and block an escape route within minutes.
Portable extinguishers support a wider fire safety plan. They do not replace suitable fire alarm systems, emergency lighting, fire doors, evacuation procedures or a suitable and sufficient fire-risk assessment.
Understanding UK fire classes
UK fire classes describe the fuel involved in a fire. The main classes are:
Class A: ordinary combustible materials
Class A fires involve solid materials such as:
- Wood
- Paper
- Cardboard
- Textiles
- Many types of plastic
Water extinguishers are commonly used for Class A risks. Foam extinguishers may also be suitable where the unit is rated for Class A.
Typical locations include offices, schools, shops, homes, warehouses and workshops.
Do not assume that a water extinguisher is suitable for every fire in the room. Check for other risks, including electrical equipment, flammable liquids and cooking appliances.
Class B: flammable liquids
Class B fires involve liquids that can burn, including:
- Petrol and diesel
- Paints
- Solvents
- Cleaning chemicals
- Oils that are not classed as cooking oils
Foam extinguishers are commonly used for Class B risks. Dry powder and carbon dioxide may also be suitable for some liquid fires, depending on the specific product and risk assessment.
Do not use a water extinguisher on a flammable liquid fire. Water can spread the burning liquid and make the situation worse.
Class C: flammable gases
Class C fires involve flammable gases such as:
- Propane
- Butane
- Methane
- Some industrial gases
Dry powder extinguishers are commonly associated with Class C risks. However, extinguishing the flame does not remove the danger. If the gas supply continues, an unburned gas cloud can form and ignite later.
Only trained and competent people should deal with a gas fire. The priority is to isolate the supply if it can be done safely, raise the alarm and evacuate.
Class D: combustible metals
Class D fires involve combustible metals such as magnesium, sodium, potassium and some forms of aluminium or lithium.
These fires require specialist extinguishing media. Standard water, foam, carbon dioxide and general-purpose powder extinguishers may be unsuitable or dangerous.
If your premises use, store or process combustible metals, obtain a specialist fire-risk assessment. Do not select a Class D extinguisher based on colour alone.
Class F: cooking oils and fats
Class F fires involve high-temperature cooking oils and fats. They are common risks in:
- Commercial kitchens
- Restaurants
- Cafes
- Hotels
- Care homes
- School kitchens
- Food production areas
Wet chemical extinguishers are designed primarily for Class F fires. They work by cooling the oil and forming a layer that helps prevent re-ignition.
Never use water on a hot cooking oil fire. Water can instantly turn to steam and cause burning oil to erupt out of the appliance.
Do not move a burning pan or fryer. Turn off the heat only if this can be done without risk. Raise the alarm, evacuate and call 999.
Electrical equipment is a risk category, not a fire class
Electrical equipment is often described as an “electrical fire class”. Technically, it is not a separate fire class in the same way as Class A, B, C, D or F.
Electrical equipment is a risk category because the presence of live electricity affects which extinguishing agent can be used safely. Once the power is isolated, the fire should be assessed according to the material burning.
Examples include:
- Computers and servers
- Machinery
- Distribution boards
- Sockets and wiring
- Printers and appliances
- Battery charging equipment
Never use a standard water extinguisher on live electrical equipment. Water can conduct electricity and create a serious shock risk.
Standard foam and wet chemical extinguishers should also not be used on live electrical equipment unless the individual extinguisher is specifically tested, marked and approved for that application.
Carbon dioxide extinguishers
Carbon dioxide, or CO₂, extinguishers are commonly used for live electrical equipment and some Class B liquid risks. They do not leave a powder or foam residue, making them useful around sensitive office and electronic equipment.
CO₂ extinguishers still require care. The discharge horn becomes extremely cold, and the gas can present a risk in poorly ventilated areas. Follow the label and use only if trained.
Dry powder extinguishers
ABC dry powder extinguishers can cover Class A, B and C risks. They may also be suitable for certain live electrical risks, usually within the voltage limit stated on the label.
Powder can reduce visibility, contaminate machinery and affect breathing. It may not be the best choice inside an occupied building, even where it is technically suitable.
Water mist extinguishers
Some water mist extinguishers are tested for several fire risks, including certain electrical applications. Do not rely on appearance or general claims. Check that the unit is specifically marked for the intended risk and follow the manufacturer’s instructions.
Fire extinguisher types at a glance
| Extinguisher type | Common applications | Important warning |
|---|---|---|
| Water | Class A materials such as wood, paper and textiles | Never use on live electrical equipment or flammable liquids |
| Foam | Class A and Class B risks where the label confirms suitability | Do not use on live electrical equipment unless specifically approved |
| Dry powder | Class A, B and C risks, with some electrical applications | Can reduce visibility and leave residue; follow voltage and label limits |
| CO₂ | Electrical equipment and some Class B risks | Take care with the cold horn and ventilation |
| Wet chemical | Class F cooking oils and fats | Never use on live electrical equipment |
| Water mist | Multiple risks where specifically tested and labelled | Confirm the exact approved applications before use |
Colour panels are useful for identification, but colour alone is not enough. Check the label, fire rating and instructions on every extinguisher.
Positioning, signage and access
A suitable extinguisher is only useful if people can find and reach it.
Extinguishers should be:
- Located where the fire-risk assessment identifies them as necessary
- Clearly visible and easy to access
- Positioned near exits or escape routes where appropriate
- Mounted or placed securely
- Kept away from stored goods and obstructions
- Protected from damage, extreme conditions and contamination
- Supported by clear fire safety signage
Do not hide extinguishers behind stock, furniture or doors. Do not place them where someone would need to pass close to a fire to reach them.
The number and type required depend on the building layout, occupancy, activities, equipment and foreseeable fire risks. A small office, commercial kitchen, workshop and industrial unit will not have the same requirements.
Inspection and servicing
Fire extinguishers require regular attention. A visual check should identify obvious problems such as:
- Missing or damaged equipment
- Blocked access
- Incorrect location
- Missing signage
- Corrosion or leakage
- Damaged hoses, pins or handles
- Low pressure where a gauge is fitted
- Evidence of discharge or tampering
- Expired or illegible labels
Professional servicing should be arranged at appropriate intervals and in line with current guidance, manufacturer requirements and the needs of the premises. Keep records of inspections, servicing, defects and corrective action.
A service visit should not only check the extinguisher. It should also consider whether the equipment remains suitable for the current risk. Changes to the building, occupancy, machinery, storage or cooking facilities may require different protection.
Training and fire-risk assessment
Employees should know:
- How to raise the alarm
- Where the escape routes are
- Where extinguishers are located
- Which extinguisher types are present
- When not to tackle a fire
- Where to assemble after evacuation
Only trained people should attempt to use a portable extinguisher. Training must reinforce that evacuation comes first.
The responsible person for a workplace or other non-domestic premises must carry out and regularly review a fire-risk assessment. This includes identifying hazards, protecting people at risk, providing suitable fire safety measures and planning for emergencies.
Read the current GOV.UK workplace fire safety responsibilities and the Welsh Government fire safety guidance for further information.
How Dragon can help in North Wales
Dragon Security & Electrical is a fire safety and electrical contractor supporting domestic, commercial, industrial and public sector premises across North Wales and beyond.
Our fire services include:
- Fire extinguisher installation
- Inspection and maintenance
- Fire-risk assessment and signage
- Fire alarm systems
- Fire alarm installation and servicing
- 24/7 fire alarm monitoring
- Emergency lighting
- Electrical inspection and testing
- Planned preventative maintenance
Our engineers can review your existing arrangements, identify gaps and recommend practical improvements based on your premises and risks.
Explore our fire services or electrical services. For advice or to arrange a site visit, call Dragon on 01492 330330 or use our contact page.
Fire extinguisher selection should never be guesswork. Choose equipment based on the fire risks, keep it accessible, service it properly and make sure everyone knows that evacuation is the first priority.