Cooking oil fires are one of the most serious fire risks in commercial kitchens across the UK. Restaurants, cafés, takeaways, and catering facilities often operate with deep fat fryers and high volumes of hot oil, creating conditions where even a brief lapse in attention can spark a dangerous fire. For businesses, knowing which fire extinguisher to use on cooking oil fires is not only a matter of safety but also a legal requirement under UK fire safety regulations.
This guide explains why standard extinguishers are unsuitable, how wet chemical extinguishers work, and what commercial kitchen operators need to know to stay compliant and protect staff.
The Quick Answer
The correct fire extinguisher for cooking oil fires in commercial kitchens is a wet chemical extinguisher, designed specifically for Class F fires. These extinguishers cool the oil and create a barrier that prevents re-ignition, making them the only safe and effective option.
Water, foam, CO₂, and powder extinguishers should never be used on cooking oil fires. In a professional kitchen, using the wrong extinguisher could cause the fire to spread instantly, endangering staff and property.
Why Cooking Oil Fires Are Different
Cooking oils and fats burn at extremely high temperatures. Once oil ignites, it cannot be put out by conventional means. Pouring water on hot oil, for example, causes an explosive reaction as the water instantly vaporises, propelling burning oil across the kitchen.
In commercial kitchens, the risks are greater because:
Deep fat fryers hold large volumes of oil at ignition-prone temperatures
Flames can quickly spread to overhead canopies, ductwork, and other appliances
Staff often work in confined spaces where escape routes may be limited
Busy service hours increase the risk of distraction or error
Because of these unique hazards, commercial premises must be equipped with the right fire-fighting equipment, including wet chemical extinguishers.
Class F Fires and Wet Chemical Extinguishers
What is a Class F Fire?
Under British and European fire classification, Class F covers fires involving cooking oils and fats. These fires are distinct from Class B (flammable liquids like petrol) because oils burn at much higher temperatures, requiring a different extinguishing method.
How Wet Chemical Extinguishers Work
Wet chemical extinguishers contain a potassium solution that reacts with burning oil in two ways:
Cooling – the chemical lowers the oil’s temperature below ignition point.
Saponification – the solution forms a soapy, foam-like barrier over the surface of the oil, cutting off oxygen and preventing re-ignition.
This dual action makes them uniquely effective against deep fat fryer fires and other oil-based blazes.
Where Wet Chemical Extinguishers Should Be Installed
In commercial kitchens, wet chemical extinguishers should be located:
Close to deep fat fryers, but at a safe distance so they remain accessible if a fire starts
Mounted on the wall with clear signage
Alongside a fire blanket, which may be used for very small pan fires
For compliance, extinguishers should be installed by a competent professional and maintained annually under BS 5306 standards.
Legal Requirements for Commercial Kitchens
Under the Regulatory Reform (Fire Safety) Order 2005, employers and business owners have a legal duty to:
Carry out a fire risk assessment
Provide appropriate firefighting equipment
Train staff in emergency procedures
For any premises with cooking oils or deep fat fryers, this means installing wet chemical extinguishers as standard. Failure to comply can result in prosecution, fines, and in serious cases, closure of the business.
The British Standard BS EN 3 also sets requirements for extinguisher types and ratings. Wet chemical extinguishers suitable for deep fat fryers carry a Class F rating, often expressed in litres of oil they can safely extinguish (for example, a 75F rating means it can deal with 75 litres of oil). Businesses should ensure the extinguisher installed matches the volume of fryers in use.
Training and Staff Awareness
Even with the correct extinguisher, staff must know how and when to use it. Key training points include:
PASS technique – Pull the pin, Aim at the base, Squeeze the handle, Sweep side to side.
Escape awareness – Only attempt to fight a fire if your back is to a clear exit.
Size limits – Extinguishers are effective only on small, contained fires. If the fire spreads beyond the fryer, staff should evacuate immediately.
Protective equipment – In some cases, protective gloves and aprons can reduce the risk of burns during firefighting.
Regular fire drills and refresher training should be part of staff induction and ongoing safety programmes.
Common Misconceptions and Mistakes
Many kitchen fires become more dangerous because staff instinctively try the wrong method. The most common mistakes include:
Using water – causes violent flare-ups and spreads burning oil.
Using CO₂ extinguishers – these may briefly push flames down but do not cool the oil, leading to rapid re-ignition.
Using dry powder extinguishers – while effective on electrical fires, powder can scatter burning oil and contaminate food preparation areas.
Covering large fires with blankets – fire blankets are only suitable for small pan fires, not deep fat fryer incidents.
Beyond Extinguishers: Prevention and Suppression Systems
While extinguishers are essential, prevention remains the best protection. Businesses should implement strict controls, including:
Thermostats and safety cut-offs on deep fat fryers
Regular cleaning of hoods and ducts to prevent grease build-up
Clear housekeeping to remove combustible materials from the cooking area
Routine staff training on safe fryer use and emergency procedures
For larger kitchens, especially in restaurants and hotels, installing an automatic fire suppression system (such as Ansul systems) provides added security. These systems detect fires above fryers and automatically release wet chemical agents, often required by insurers for high-risk premises.
Conclusion
For commercial kitchens in the UK, the message is clear: only wet chemical extinguishers are suitable for cooking oil fires. They are specifically designed to combat Class F fires found in deep fat fryers and other catering equipment, providing both cooling and re-ignition prevention.
Every restaurant, café, takeaway, and catering business must ensure these extinguishers are installed, maintained, and backed up by proper staff training and fire risk assessments. By following these requirements, businesses not only meet legal obligations but also protect lives, property, and livelihoods.
Remember: if a cooking oil fire is too large or spreading, the safest action is to evacuate immediately, call 999, and let the fire service take control.
