The importance of cleaning kitchen extract ductwork to prevent fires

James McConville

James McConville
Senior Consultant, Assurity Consulting
13th August 2019

The extract systems in a kitchen are probably one of the biggest fire hazards in this working environment.

The greasier the food and as the volume of cooking increases, the likelihood of grease build-up also increases. It is essential this is considered when planning a cleaning regime for the extract systems. As the grease gets extracted from above the cooking hobs not all of it will get extracted out by the filters. Much of the grease will collect in the ductwork and build up over time. This grease is extremely flammable and in the right conditions can cause a fire.

There are on average 24,000 fires in commercial properties each year and 24% of those are the result of cooking and extract systems. Insurance companies are paying out, on average, £65 million a year on kitchen extract fires. Increasing numbers of insurance companies are now refusing to pay for damage caused by kitchen fires as a result of poor cleaning of the extract systems.

Many of the kitchen fires you hear about on the news would probably have been the result of the extract systems not being cleaned at the right frequency or sufficiently. A good example of this was the El Vaquero restaurant, Whetstone where over sixty people were evacuated due to a kitchen fire which left the kitchen and roof of the building with heavy damage. The Times reported that the fire is believed to have been caused by the accidental ignition of grease and fat through cooking, which spread to the ducting system.

Firefighters had to cut away ductwork to access the fire to put it out. The fire brigade said: “Restaurant and take-away owners should always take care to make sure their extraction systems are kept clean as a build-up of fat and grease within the filters can lead to a fire.”  The restaurant lost a significant amount of business due to the fire and having the correct cleaning regime in place would have prevented this.

If the kitchen is heavily used (12-16 hours a day) or you are cooking greasy food, then the systems should be cleaned every three months. For moderately used kitchens (6-12 hours a day) then six-monthly cleaning would be sufficient. Any less than annual cleaning of the ductwork and extract is not enough. Pre and post photos should be provided by your cleaning contractor to confirm that your cleaning regime is sufficient. There are various tests that can be carried out to measure the thickness of the grease or dust, which will help you ascertain the correct cleaning frequency.  It is also essential this area of fire prevention is covered in your fire risk assessment.  This would be well worth a check.   

A fire in a kitchen can lead to prosecution and possible fines and imprisonment and in many cases, a business does not recover. To avoid being one of those unfortunate businesses, please call us and ask to speak to either our fire safety or food safety teams or email us at