According to a 2017 report from the National Fire Protection Association (NFPA), fire departments respond to over 7,000 restaurants and bar fires every year1. Although the cooking equipment is the leading cause of those fires, 7
out of 10 did not spread beyond the place of fire origin. The NFPA restaurant standard, NFPA 96, requires both a kitchen system and Class K extinguishers for the cooking areas. A logical conclusion is that the kitchen systems and the extinguishers
are doing a good job of protecting employees and patrons and keeping property losses to a minimum. Here is what you need to know regarding the Class K extinguishers that are installed as a backup to the restaurant system.
Class K fire extinguishers are intended for installation in restaurants and other buildings with commercial cooking operations, like office buildings, schools, and universities with cafeterias. This type of extinguisher is specifically designed
for fires in cooking appliances where oil is used as the cooking medium. Class K extinguishers are required to be installed by state fire codes across the country. There are no substitutes. Only Class K extinguishers are permitted for
this application.
Class K Extinguishing Agent
The agent in a Class K extinguisher is called “wet chemical”. When discharged during a fire, a foam is formed that extinguishes oil fires by smothering (eliminating contact with air). Interestingly, it is the same agent as used in the restaurant
extinguishing system. The agent is discharged from the extinguisher through a special nozzle that creates a fine mist spray that gently lands on the surface of a grease fire without splashing. Although the agent contains about 98% water,
there is a special additive that chemically reacts with the fat in the cooking oil to create a thick foam blanket that floats on the surface of the oil.
How Class K Extinguishers Work
Unlike conventional extinguishers that typically require a sweeping action, the thick foam blanket is created almost instantaneously when the mist spray hits the oil surface. Since it is floating on the surface of the oil, it naturally spreads
across the top of the oil. This action suffocates the fire, meaning that the oil vapors cannot reach the air and continue burning. On the other hand, upon extinguishment, the oil temperature is still elevated and will spontaneously ignite
if exposed to air. Therefore, it is extremely important that the foam blanket be left undisturbed until the oil has a chance to cool.
Minimum Number of Class K Extinguishers
Every commercial kitchen that uses oil as a cooking medium must have at least one Class K extinguisher. But many larger kitchens must have more than one. That is because the maximum travel distance from the cooking appliance hazards to a Class
K extinguisher cannot exceed 30 ft. Other factors that will drive the need for more extinguishers are visibility, accessibility, and cooking area appliance locations. Since life safety is paramount, technicians will often install multiple
Class K extinguishers in strategic locations based on safety considerations and discussions with owners and restaurant managers.
BL189 - Typical Class K Extinguisher Placard Required by Code
Class K Extinguisher Placards
It is necessary to have both extinguishers and a fire system for every commercial cooking operation that uses oil as a cooking medium. A placard is required to be installed at each Class K extinguisher to inform the kitchen staff that the
extinguisher is only to be used after the suppression system has been discharged. This is important because the system has an interlock that automatically shuts down the heat sources in the appliances.
The local state fire code requires restaurant employees be provided with instructions on the use of extinguishers and operation of the hood system. Not only is training required upon initial hiring of new employees, training is also required
on an annual basis for all kitchen staff.
Onsite instructions often include a walkthrough of the cooking area. As a minimum, this includes identification of each pull station for the kitchen system, Class K extinguishers, and the accompanying extinguisher placards. Once these safety
features are identified, kitchen staff need introductory and annual instructions on the following:
- How to manually operate the hood system to shut off heat sources and extinguish a fire
- Hot to notify the fire department in the event of a fire emergency
- How to effectively evacuate employees and patrons in the event of a fire emergency
- How to operate and use a Class K fire extinguisher as a backup to the hood system
Your customers with restaurants and cafeterias will appreciate that you know so much about Class K extinguishers that are installed to protect their operations. They will also appreciate your insights on how Class K extinguishers work and
what their employees need to know regarding fire safety. So, the next time you make a service call at a commercial kitchen, take time to catch up with the manager to talk about safety. You might also want to leave a copy of this article
for future reference and as a safety reminder.
1Structure Fires in Eating and Drinking Establishments, Richard Campbell, February 2017, National Fire Protection Association, https://www.nfpa.org//-/media/Files/News-and-Research/Fire-statistics-and-reports/Building-and-life-safety/oseating.pdf.