Chemical Fire Suppression Systems for Commercial Cooking

Because of changes in fire hazards in commercial kitchens, on November 21, 1994, an Underwriters Laboratories (UL)® test standard entitled UL 300, Fire Testing of Fire Extinguishing Systems for Protection of Restaurant Cooking Areas® went into effect.

UL® developed a series of fire tests for pre-engineered chemical suppression systems designed to duplicate the potential commercial cooking fire hazards. These tests establish specific requirements and limitations of extinguishing agents, fire detection, piping, nozzle coverage and more for each manufacturer who submits its system for UL® testing.

The Impact of Temperature on Fats and Oils

Commercial cooking operations, appliances and supplies have changed greatly since the 1960’s. These changes have altered the fire hazards in cooking areas. Health concerns have reduced the use of lard. Efforts to cook faster have increased the use of insulated, more efficient fryers that heat faster and cool slower.

Restaurant suppliers now estimate that 70-75% of all commercial kitchens use vegetable oils for frying in high-efficiency fryers. Lard has a high percentage of saturated fat and a lower ignition temperature (550-600 F), whereas vegetable oils have a very low percentage of saturated fat and a higher ignition temperature (685 F).

The extinguishing agent in earlier systems was alkaline based, which when combined with fat, produced a soapy blanket, cutting off the oxygen supply and containing the fire until the fuel was cooled below its ignition temperature.

A similar fire involving vegetable oils creates a different set of circumstances. With only a limited amount of fat, the soapy action is greatly reduced and the higher temperature of such fires, enhanced by the insulation in a high efficiency fryer, causes the soap blanket to break down. Thus, the extinguishing capability of the earlier fire suppression system is reduced.

Chemical Fire Suppression System Change Guidelines

Over the last few years, there have been questions about changing an existing dry chemical extinguishing system to a listed UL 300® wet chemical system. Updating your fire suppression system should be considered if any of the following has occurred:

• The hazard being protected has changed
• Newer energy efficient cooking appliances have been installed, which keep cooking oils and metal appliances hotter for longer
• Vegetable oils are being used for cooking in place of animal fat
• There are no longer parts or agent available for service of the existing system, thereby voiding its listing