Class K Extinguishers

 

Fire extinguishers for the protection of cooking media fires (vegetable or animal oils and fats) traditionally required a minimum 40-B rated sodium bicarbonate or potassium bicarbonate dry chemical extinguisher as specified for extra (high) hazard requirements of NFPA 10. The evolution of high efficiency cooking appliances and the change to hotter-burning vegetable shortening has created a more severe fire hazard and has prompted the creation of a new classification of fire, Class K. Testing by Underwriters Laboratories has shown that wet chemical extinguishers with a K classification have several times the extinguishing capability of a 40-B rated sodium bicarbonate or potassium bicarbonate extinguisher in controlling cooking fires.

 

The Class K extinguisher offers improved fire control for this type of hazard by:

(1) Creating a foam blanket by saponifying (converting into a soap) the hot cooking oils.

(2) Cooling both the appliance and the hot cooking oils.

(3) Offering improved visibility during fire fighting.

(4) Minimizing splash hazard.

(5) Providing easier clean-up than when using dry chemical agents.

Accordingly, the Fire Equipment Manufacturers’ Association, Inc. [FEMA] recommends that all Class B extinguishers used to protect cooking appliances/kitchens be replaced by the owners with Class K extinguishers as soon as possible. The travel distance of 30 feet as previously described in NFPA 10 is still recommended.

 

Class K Rating Tests

 

Class K rated fire extinguishers are rated for their ability to fight fire in commercial cooking environments. The newest version of the UL Standard 300, Standard for Fire Testing of Fire Extinguishing Systems for Protection of Restaurant Cooking Areas, is more restrictive than previous tests in commercial cooking media. The fuel used must be new vegetable shortening or oil with an anti-foaming agent and an auto-ignition temperature of 685 degrees Fahrenheit (362.7 degrees Celsius) or higher. Tests are performed on four types of cooking appliances: fryers, ranges, griddles, and woks. Manufacturers of hood extinguishing systems are now using the potassium-based liquid agents (potassium acetate, potassium carbonate, and potassium citrate) for installation in commercial kitchens because sodium bicarbonate is no longer used.

 

Class K Extinguisher Distribution Factors

 

In the working environment of commercial cooking occupancies, fire is always present. Employees in such areas are charged with the responsibility to maintain appropriate cooking temperatures to ensure safety. Because employees are in various levels of training for their jobs and because there is potential of fire hazards occurring in an assembly area (dining room), NFPA 10 has assigned a more restrictive distance requirement. In areas where Class K fires are likely, the maximum travel distance from the hazard to the extinguisher is reduced to 30 feet (10 m).

 

In addition to proper selection and distribution, effective use of fire extinguishers requires that they be readily visible and accessible. Proper placement of extinguishers should provide the following:

(1) Extinguishers should be visible and well marked.

(2) Extinguishers should not be blocked by storage or equipment.

(3) Extinguishers should be near points of egress or ingress.

(4) Extinguishers should be near normal paths of travel.

(5) Extinguishers should be placed so that all personnel can access it.

(6) Extinguishers with a gross weight not exceeding 40 pounds (18 kg) should be installed so that the top of the extinguisher is not more than 5 feet (1.5 m above the floor.

(7) Extinguishers with a gross weight greater than 40 pounds (18 kg), except wheeled types, should be installed so that the top of the extinguisher is not more than 3 ½ feet (1 m) above the floor.

(8) The clearance between the bottom of the extinguisher and the floor should never be less than 4 inches (100 mm).

 Attacking Class K Fires

 

Class K (cooking media) fires are particularly difficult to extinguish because of their tendency to reignite after the fire has been extinguished. It has been discovered that although a Class K fire may have been extinguished properly with a dry chemical, the fuel changes chemically and reaches auto-reignition at a lower temperature. For this reason, only an extinguisher with a Class K rating is recommended for use on this type of fire. The initial attack on a Class K fire with an appropriately marked Class K extinguisher is similar to other types of attack. Begin application from a distance of 10-12 feet (3.1 to 4 m) away from the burning material, hold the application wand at the edge of the flames, and coat the surface of the material with a side-to-side sweep. Continue to apply agent until the fire extinguisher is completely empty. Extinguishment takes place through cooling the fuel. It is the innate cooling quality of the agent, along with its ability to form soapy foam (saponification) that prevents the fuel from reaching a lower reignition temperature.

  

NFPA 10 – 2002 edition and Class K Extinguishers

 

The 2002 edition of NFPA 10 specifically states:

 

3.3.4 Classifications for Fires.

 

3.3.4.5 Class K Fires. Fires in cooking appliances that involve combustible cooking media (vegetable or animal oils and fat).

 

4.2 Selection by Hazard

 

4.2.1.5 Fire extinguishers for the protection of Class K hazards shall be selected from types that are specifically listed and labeled doe use on Class K fires.

 

4.3 Application for Specific Hazards.

 

4.3.2 Class K Fire Extinguishers for Cooking Oil Fires. Fire extinguishers provided for the protection of cooking applicances that use combustible cooking media (vegetable or animal oils and fats) shall be listed and labeled for Class K fires. Class K fire extinguishers manufactured after January 1, 2002 shall not be equipped with “extended wand-type” discharge devices.” The standard specifically addresses a manufacturing requirement and cut-off date, not any requirement that could be considered retroactive, or any requirement for placement of extinguishers that were made prior to that date.

 

4.3.2.1 Fire extinguishers installed specifically for the protection of cooking applicances that use combustible cooking media (vegetable or animal oils and fats) prior to June 30, 1998, shall not be required to comply with 4.3.2. (Also see 4.3.2.3)

 

4.3.2.2. A placard shall be conspicously placed near the extinguisher that states the fire protection system shall be activated prior to using the fire extinguisher.

 

There has also been some confusion that statements made in the Annex section of NFPA 10 represent new requirements. The Annex material is for informational purposes only and is not considered to be part of the standard. Again, NFPA 10 specifically states:

 

"Annex A is not a part of the requirements of this NFPA document but is included for informational purposes only.”

 

Another new requirement that is important to note is the specific replacement of existing dry chemical extinguishers. NFPA 10 2002 edition states:

 

4.3.2.3 Existing dry chemical extinguishers without a Class K listing that were installed for the protection of Class K hazards shall be replaced with an extinguisher having a Class K listing when the dry chemical extinguishers become due for either a 6-year maintenance or hydrostatic test.

 

5.7 Fire Extinguisher Size and Placement for Class K Fires.

 

5.7.1 Class K fire extinguishers shall be provided for hazards where there is a potential for fires involving combustible cooking media (vegetable or animal oils and fats).

 

5.7.2 Maximum travel distance shall not exceed 30 ft. (9.15 m) from the hazard to the extinguishers.

 

NFPA 96

 

10.1 General Requirements

 

10.1.1 Fire extinguishing equipment for the protection of grease removal devices, hood exhaust plenums, and exhaust duct systems shall be provided.

 

10.1.2 Cooking equipment that produces grease-laden vapors and that might be a source of ignition of grease in the hood, grease removal device, or duct shall be protected by fire-extinguishing equipment.

 

10.2 Types of Equipment

 

10.2.1 Fire-extinguishing equipment shall include both automatic fire-extinguishing systems as primary protection and portable fire extinguishers as secondary backup.

 

10.2.2 A placard identifying the use of the extinguisher as a secondary backup means to the automatic fire-extinguishing system shall be conspicuously placed near each portable fire extinguisher in the cooking area.

 

10.2.2.1 The language and wording of the placard shall be approved by the authority having jurisdiction.

 

10.10.1 Portable fire extinguishers shall be installed in kitchen cooking areas in accordance with

NFPA-10 and shall be specifically listed for such use.

 

KITCHEN FIRE-EXTINGUISHING SYSTEMS

NFPA 101, Life Safety Code references other NFPA standards for compliance in certain areas. This includes requirements applicable to the kitchen exhaust hood and fire-extinguishing systems found in NFPA 96, Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations

 

PORTABLE EXTINGUISHERS

10.10 Portable Fire Extinguishers.

 

10.10.1 Portable fire extinguishers shall be installed in kitchen cooking areas in accordance with NFPA 10 and shall be specifically listed for such use.NFPA 10, Standard for Portable Fire Extinguishers

 

5.7 Fire Extinguisher Size and Placement for Class K Fires.

 

5.7.1 Class K fire extinguishers shall be provided for hazards where there is a potential for fire involving combustible cooking media (vegetable or animal oils and fats).

 

5.7.2 Maximum travel distance shall not exceed 30 ft (9.15 m) from the hazard to the extinguishers.

 

10.2.2 A placard identifying the use of the extinguisher as secondary backup means to the automatic fire-extinguishing system shall be conspicuously placed near each portable fire extinguisher intended to be used for protection in the cooking area.

 

What this means. A portable K-type fire extinguisher is required in the kitchen. A sign describing the use of the extinguisher must be placed near the extinguisher.