Fire Prevention: Commercial Cook Line Extinguishment Systems

Short Course in Modern Commercial Kitchens
Anyone who walks into a busy commercial kitchen these days has seen the skillful use of flame and heat to prepare meals ranging from sizzling steaks to fried seafood. Backyard gas barbeque cooks handle the same exercise on a smaller scale. On both ends of this spectrum, the cooks get first hand experience with the fire hazards associated with animal fats rendering from hot meat and flaming ignition of common vegetable based cooking oils.

It is with good reason that barbeque tools have long handles.

What is less well known to the average person is the fire hazard created by common vegetable oils and vegetable based shortenings in commercial kitchens. The word in the restaurant industry is that these products are even more dangerous than their animal fat counterparts.

Here's the rub.

Some people in the food service industry still don't seem to appreciate the need to change out the automatic hood extinguishment system when using the vegetable based cooking oils and shortenings. This ignorance or false economy has led to a continuing series of restaurant fires and large property insurance settlements.

Health/Conservation Concerns Forced a Change
For twenty years medical researchers have linked saturated fats in certain foods, especially meats, and the coronary artery disease that is the leading cause of death in this country. In response to this situation, over a decade ago, the food service industry began switching from animal based shortenings and fats to vegetable based shortenings and fats in cooking and frying operations. Today, this switchover is nearly complete.

At about the same time, cook line equipment manufacturers created a new generation of "energy efficient" appliances that were more heavily insulated and operated at higher temperatures. While energy was conserved, experience also showed when a hostile fire began the "efficient" units took longer to cool down.

The vegetable fat and shortening fires were much more difficult to extinguish.

Big Problem
The latest statistics from the National Fire Protection Association indicate that in an average year there are 11,100 structure fires in eating and drinking establishments in the United States resulting in six civilian deaths, 189 civilian injuries and $163.1 million in direct property damage.¹

Half of these fires start in the kitchen. Some type of cooking equipment caused two of every five fires in eating and drinking establishments. Deep Fat fryers ranked second in fires in eating and drinking establishments and first among cooking equipment in dollar loss.² The other major causes of cook line kitchen fires in these establishments included Stoves (#1), Ovens (#3), Open Fired grills (#4) and Grease hood or ductwork (#5)³. All of these major kitchen fires began in cooking appliances normally found on a cook line beneath an exhaust canopy hood equipped with some type of automatic fire suppression system.

What happens after a flaming ignition grows beyond acceptable limits is dependent on a short list of very important factors; the design, scheduled cleaning and maintenance of the cook line and its exhaust hood, training of personnel and the adequacy of the automatic fire suppression system in place.

Fire Prevention Measures
One distinctive difference between animal and vegetable cooking oils and shortenings is in the type of extinguishment agent needed to put out a fire should it develop out of control. Where the common ABC extinguisher (Sodium Bicarbonate and flowing agents) is usually effective against animal fat and common combustible fires, this class of extinguisher, and even wet pipe sprinklers, are ineffective against vegetable fat fires.

Fires in cook line appliances using vegetable based shortenings and fats require an entirely new class of extinguishment - the so-called wet chemical agent. This new system creates an effect called "sponification" which acts to blanket the surface of burning oil with thick foam effectively reducing the release of hot fumes. At the same time, spraying the "wet" water based chemical helps to cool the hot oil and surrounding surfaces.

The new wet chemical systems require greater nozzle density, lower nozzle height over the cooking surfaces, increased pressure and larger agent droplet size over the older systems. In a fully code compliant system each appliance on the cook line must have a 450? F fusible link over its cooking surface.

Should a fire grow out of control in a given appliance, the fusible link above it on a tensioned cable is designed to melt causing a mechanical lever to drop and activate activate the suppression system. At the same time the extinguishment agent is released an interlock device cuts off the fuel gas supply to all appliances on the cook line.

Properly installed and maintained these wet chemical systems work surprisingly well.

There are other safeguards built into a code compliant cook line that help to reduce the threat of a hostile fire extending beyond the cook line. For example, obviously hazardous appliances such as deep fat fryers must be physically isolated from nearby sources of open flame such as range top gas elements. Also, metal plates called baffles must be installed between individual appliances to help channel migration of potentially ignitable vapors away from potential sources of ignition such as gas flames.

The reason for this is obvious when you consider that some appliances such as deep fat fryers operate at temperatures above the flash point of the oils they use.

Another fire prevention safeguard is that anytime a commercial cook line is located against a wall it must have a stainless steel back plate installed with an air gap between its rear and the adjoining wall and a 16 gauge steel exhaust hood and ductwork with welded seams that meets strict engineering and code requirements. The hood must also be equipped with an automatic extinguishment system that is suitable for the cook line it protects.

Today's fire prevention codes, in particular, NFPA 96 (Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations) and NFPA 17A (Standard for Wet Chemical Extinguishing Systems) require a more aggressive type of fire suppression system suited for the increased fire hazard associated with vegetable oils and shortenings.. UL 300 1994 mandates the performance standards for fire control systems above cook lines.

Underwriters armed with these facts should always be certain that any eating and drinking establishment that they bind has a cook line fire control system that is fully compliant with the fire prevention and control standards specified in these three codes. You should also verify that the regular cleaning, testing and maintenance of the system required by the codes are being performed.

When the hammer drops, the fire control system's performance will be the difference between a major loss and a minor inconvenience.

¹Selections from The U.S. Fire Problem Overview Report: Leading Causes and Other Patterns and Trends Eating and Drinking Establishments. 2001 p.107.
²Ibid p. 108
³Ibid p. 111