Healthier Cooking Equals Hotter Fires
America’s eating habits are changing. For health reasons, we are selecting foods with less fat and cholesterol, but this has also created a fire danger. Many commercial kitchens have switched from cooking with animal fat, such as lard, to using fat-free vegetable oils in fryers. Vegetable oils burn hotter than animal fat, so vegetable oil fires are also hotter and more difficult to extinguish. Lard high in saturated fats, was usually protected by a dry chemical extinguishing system. This worked well as the dry chemical would combine with the fatty acids, in a process known as “saponification,” to create a soap blanket or foam on the surface of the grease that smothered the fire. This blanket remained in place long enough after extinguishment to prevent the fire from re-igniting.
With the use of vegetable oils, the dry chemical systems were no longer as effective in controlling or extinguishing a fire. Vegetable oils have only a limited amount of fatty acids to “saponify,” resulting in a thinner soap blanket forming when combined with the dry chemical. The thinner soap blanket breaks down before the grease can cool and the fire would re-ignite. When the oil re-ignites, there is no longer a charged suppression system to extinguish it which leads to fires that cause a much greater degree of damage to restaurants.
A classic scenario for a restaurant cooking fire is when a high-efficiency fryer overheats and ignites the vegetable oil within. The suppression system fails to operate and the grease in the exhaust hood ignites, allowing the fire to spread into the grease coated duct-work leading into the sub ceiling. The heat emanating from the duct-work ignites the wood structure and leads to a total loss of the restaurant. There are three things you can actively do to help prevent this scenario:
- Per NFPA 10, Class K fire extinguishers must be provided for hazards where there is a potential for fires involving combustible cooking media such as vegetable fats, animal fats or oils. The maximum travel distance from the hazard to the extinguishers must be no more than 30 feet.
- If you are using vegetable oil in your fryers, make sure your fire suppression system and fire extinguishers are designed to put out these hotter fires. Current codes require a UL 300 listed hood fire extinguishing system for cooking that involves grease laden vapors. K-rated fire extinguisher is required in a commercial kitchen.
- Keep with your regular frequency of kitchen exhaust cleanings. 1/8” of grease anywhere in the exhaust system is required to be cleaned. Make sure your kitchen exhaust cleaning professional has you on the proper frequency and is familiar with your accumulation rate.