Page 29 - OHS, April 2022

for Class B fires should be identified by a square containing the letter “B.”
Class C fire extinguishers are used on fires that involve live electrical equipment, which require the use of electrically non- conductive extinguishing agents. (Once the electrical equipment is de-energized, extinguishers for Class A or B fires may be used.) Extinguishers that are suitable for Class C fires should be identified by a circle containing the letter “C.”
Most fire extinguishers found in busi- nesses are of the A, B and C classification of extinguisher.
Class D fire extinguishers are used on combustible metals—such as magnesium, titanium, sodium, etc.—which require an extinguishing medium that does not react with the burning metal. Extinguishers that are suitable for Class D fires should be identified by a five-point star containing the letter “D.”
Class K fire extinguishers are used on fires involving cooking media— fats, greases, oils, etc.—in commercial cooking sites such as restaurants. These fire extinguishers work on the principle of saponification. Saponification takes place when alkaline mixtures—such as potassium acetate, potassium citrate,
or potassium carbonate—are applied to burning cooking oil or fat. The alkaline mixture combined with the fatty acid creates a soapy foam on the surface that holds in the vapors and steam, extinguishing the fire. These extinguishers are identified by the letter K.
Labeling
Fire extinguishers are labeled so users can quickly identify the classes of fire on which the extinguisher will be effective. The marking system combines pictographs of both recommended and unacceptable extinguisher types on a single identification label.
Also located on the fire extinguisher label is the UL rating. The UL rating is broken down into Class A and Class B:C ratings. Numerical ratings allow you to compare the relative extinguishing effectiveness of various fire extinguishers. For example, an extinguisher that is rated 4A:20B:C indicates the following:
1. The A rating is a water equivalency rating. Each A is equivalent to 1 1/4 gallons of water. 4A = 5 gallons of water.
2. The B:C rating is equivalent to the amount of square footage that the extin- guisher can cover, handled by a profes- sional. 20 B:C = 20 square feet of coverage.
3. C indicates it is suitable for use on electrically energized equipment.
When analyzing these ratings, note there is not a numerical rating for Class C or Class D fires. Class C fires are essentially either a Class A or a Class B fire involving energized electrical equipment where the fire extinguishing media must be non- conductive. The fire extinguisher for a Class C fire should be based on the amount of the Class A or Class B component. For extinguishers used on a Class D fire, the relative effectiveness is detailed on the extinguisher nameplate for the specific combustible metal fire for which it is recommended.
Location
OSHA (2002) requires that employers select and distribute fire extinguishers based on the classes of anticipated workplace fires and also on the size and degree of the hazard that would affect their use. The following charts contain the IFC requirements for classes of fires and travel distance to an extinguisher. NFPA (2022) requires Class K extinguishers to be
placed no more than 30 feet from hazard. Some local requirements may be stricter, so you should always check with the local fire marshal and underwriter for risk management. In some areas, the fire marshal will provide some assistance in
locating fire extinguishers as well. Extinguishers need to be conspicu- ously located and available in the event of a fire. They also should be located along normal paths of travel and near exits. Portable fire extinguishers that are not wheeled should be installed on the hanger or bracket supplied or placed in cabinets
or wall recesses.
The locations of fire extinguishers must
be identified so they are readily available to employees without subjecting them to injury. Height requirements for mounting extinguishers depend on the weight of the unit. If the unit weighs less than 40 pounds, it should be installed so the top of the extinguisher is no more than 5 feet above the floor. If the unit weighs more than 40 pounds, it should be installed so the top of the extinguisher is no more than 3.5 feet above the floor. At no point should the extinguisher be less than 4 inches from the floor.
OSHA (n.d.) states that instead of Class A portable fire extinguishers, an employer may use uniformly spaced standpipe systems or hose stations connected to a sprinkler system installed for emergency use by employees. Such systems must meet the respective requirements of 29 CFR 1910.1584 or 1910.159,5 that provide total coverage of the area to be protected, and that employees are trained at least annually in their use (1910.157(d)(3). While OSHA may have this exemption, it does not exempt the property for applicable adopted codes that the local jurisdiction is enforcing.
Training
OSHA (n.d.) states when the employer has provided fire extinguishers for employee use, the employer must provide an educa- tional program to familiarize employees with the principles and use of the extin- guishers. This educational program should be completed during the initial hiring and annually thereafter (1910.157(g)(1). Check with the local fire agency to see if it has a program that provides fire extinguisher training. There are also options for virtual training as well.
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