Fire Extinguisher Placement

10/3/2016

Even to this day, after numerous unfortunate incidents, stories persist where a person would arbitrarily grab a fire extinguisher (F/E) without understanding its specific purpose, limitation or proper use, and try to extinguish a fire only to succumb to the heat, flames and poisonous gases.  The problem is that so many people do not understand how crucial it is to know the specific characteristics of the fire extinguisher that one is about to use.  

First of all, F/Es are only effective during a fire’s incipient (initial) stage. Once a fire get to be large (such as an entire room is ablaze), no F/E can help and therefore the best action people can take is to immediately evacuate the area (and call the fire department!). In addition, fires are categorized differently. A Class A fire involves combustible materials (wood, cloth, paper, etc.), while a Class B fire is designed to extinguish flammable liquids, such as gasoline or grease in a frying pan. By applying a Class A F/E (typically containing water) to a Class B fire can result in the fire actually spreading, thereby increasing the risk of a disaster that could have been easily avoided. Fires that involve electrical wiring or components (i.e. appliances) are classified as Class C. The material within a Class C (carbon dioxide and dry chemical – aka mono ammonium phosphate) is non-conductive and therefore, reduces the risk of electrical shock and possible electrocution to the user. Class D fires are those fires that involve combustible metals, such as sodium, magnesium and potassium. Sodium Chloride (aka Met L-X Powder) is a common material used in Class D F/Es. Class D F/Es work due to the heat of the fire causing the dry powder to cake and form an exterior crust. This crust prevents air from contacting the burning material, thereby extinguishing the fire. It also dissipates the heat from the burning metal.  The last F/E category (and latest to hit the market) is for cooking media, such as fats, greases and oils generally found/used in commercial cooking operations. Class K 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 of fat. The alkaline mixture combined with the fatty acid create a soapy foam layer on the surface which holds in the vapors and steam and extinguishes the fire.

So after the simple A,B,C’s (and D and K) of F/E instruction, comes the numbering. F/Es are not simply labeled A, B, or C. An examination shows that there is a number in front of the “A” and “B.” These ratings come from the amount or quantity of material that can be extinguished by a single F/E. These ratings are based on tests developed by Underwriters Laboratory (UL) to determine the capability fire extinguishing material to put out a fire on wood crib (small wood structure), wood panel and excelsior (paper/wood shavings). As a rule-of-thumb, an “A” rating without any number, assumes the value of “1.” The number “1” refers to 1 ¼ gallons of water. Therefore an “A”-rating of 2 would have double a “1” capacity, thereby being equivalent to 2 ½ -gallons of water equivalence. Another way to look at this capacity is that a 1A rating meaning the F/E can put out a fire on excelsior (paper/wood shavings) equaling 6 lbs; and therefore a “2A” rating would be equivalent of extinguishing a fire on the same material of 12 lbs.  Got it?

Next is the number in front of “B.” The accepted practice for classifying B-rated F/Es is based on the area of a fire in square feet. So a 5B F/E has the capability to extinguish a fire involving a flammable liquid that is five square feet. Easy? Just so that everyone understands, there is no numerical ratings for C, D and K-fires.

Next is location. According to OSHA (29 CFR 1910.157(c)), portable F/Es can only be effective if they are installed in all areas of the workplace and readily accessible. This means hallways, laundry rooms, meeting rooms, kitchens, mechanical/electrical rooms, and near exit doors. This is in addition of knowing which type of F/E needs to be placed in the appropriate area.    The National Fire Protection Association (NFPA) recommends that locations such as offices, classrooms, and assembly halls that contain mainly Class A combustible materials have one 2-A extinguisher for every 3,000 square feet, with a maximum travel distance of 75 feet  (NFPA 10, Standard for Portable Fire Extinguishers).

Locations that contain Class B flammables, such as workshops, storage areas, research operations, garages, warehouses, or service and manufacturing areas requires that persons have access to an extinguisher within a 50-foot travel distance (29 CFR 1910.157(d)(4))

As discussed earlier, Class C extinguishers are required where energized electrical equipment is used. According to OSHA (29 CFR 1910.157(d)(5)) the extinguisher size and spacing is based on its Class A or B hazard.

Locations where combustible metal powders, flakes, shavings, or similarly sized materials are generated at least once every two weeks must install Class D portable F/Es and located not more than 75 feet from the hazard (29 CFR 1910.157(d)(6))

Locations where potential fire hazards from combustible cooking media (vegetable or animal oils and fats) exist must install Class K extinguishers at a maximum travel distance of 30 feet (NFPA 10, Standard for Portable Fire Extinguishers).

To prevent F/Es from being moved or damaged, they should be mounted on brackets or in wall cabinets with the carrying handle placed 3-1/2 to 5 feet above the floor. Larger F/Es need to be mounted at lower heights with the carrying handle about 3 feet from the floor. The location where a F/Es is located (mounted) should also be easily assessable (not blocked by a physical barrier or poor housekeeping practices) and identified (such as a posting on the wall for persons to clearly see wear a F/E is located). 

Before installing any portable F/E, check the label to be sure it is approved by a nationally recognized testing laboratory such as UL or Factory Mutual (FM) (29 CFR 1910.157(c)(2))

The following types of portable F/Es are considered dangerous or obsolete and should not be used:

1. Any extinguisher having a shell construction of copper or brass joined by soft solder and/or rivets.
2. Any extinguisher that must be turned upside down to rupture a cartridge or to start an uncontrollable pressure generating chemical reaction to expel the agent. This includes:
   1. Soda acid
   1. Foam
   1. Water-cartridge
   1. Loaded stream cartridge
3. Extinguishers that use chlorobromomethane (Halon 1011) or carbon tetrachloride as an extinguishing agent. These agents are toxic and carbon tetrachloride may cause cancer and can produce phosgene gas (used as a chemical weapon during World War I) when used on electrical fires.

Those who do not remember the past are condemned to repeat it

George Santayana