Fire Extinguishers
Fire Extinguishers
What are the Extinguisher Sizes?
What are the Extinguisher Sizes?
In the past, the sizes of fire extinguishers were determined by the amount of chemical inside of the extinguisher. Independent testing labs (Underwriters Laboratories and FM Approvals) test extinguishers to the UL/ANSI 711 Rating and Fire Testing of Fire Extinguishers for their ability to extinguish specific classes and sizes of fires. In 2002, attempts to standardize the various test protocol differences between UL and ULC were initiated. As of August 14, 2007, all fire equipment manufacturers are required to comply with the new testing standards.
Class A Extinguishers are labeled with a number from 1 to 40.The number is an expression of the extinguisher's fire-fighting effectiveness. The larger the number, the larger the fire the extinguisher can be expected to extinguish.
Class B Extinguishers are labeled with a number from 1 to 640.The number is an expression of the extinguishers fire-fighting effectiveness. The larger the number, the larger the fire the extinguisher can be expected to extinguish.
There is no numeric designation for an extinguisher's effectiveness in fighting Class C, D, or K fires.The letters C, D, or K tell you only that the unit has been rated to combat energized electrical equipment, combustible metals, or cooking oil fires.
In the past, the sizes of fire extinguishers were determined by the amount of chemical inside of the extinguisher. Independent testing labs (Underwriters Laboratories and FM Approvals) test extinguishers to the UL/ANSI 711 Rating and Fire Testing of Fire Extinguishers for their ability to extinguish specific classes and sizes of fires. In 2002, attempts to standardize the various test protocol differences between UL and ULC were initiated. As of August 14, 2007, all fire equipment manufacturers are required to comply with the new testing standards.
Class A Extinguishers are labeled with a number from 1 to 40.The number is an expression of the extinguisher's fire-fighting effectiveness. The larger the number, the larger the fire the extinguisher can be expected to extinguish.
Class B Extinguishers are labeled with a number from 1 to 640.The number is an expression of the extinguishers fire-fighting effectiveness. The larger the number, the larger the fire the extinguisher can be expected to extinguish.
There is no numeric designation for an extinguisher's effectiveness in fighting Class C, D, or K fires.The letters C, D, or K tell you only that the unit has been rated to combat energized electrical equipment, combustible metals, or cooking oil fires.
What is the Area Hazard Classification?
The class and the size of fire likely to occur in a particular area are key factors in determining the appropriate type and size of extinguisher to be used. Together, the class and size of a potential fire define the hazard for which your extinguisher installations must be designed.
The class and the size of fire likely to occur in a particular area are key factors in determining the appropriate type and size of extinguisher to be used. Together, the class and size of a potential fire define the hazard for which your extinguisher installations must be designed.
Hazard Classification: (per the National Fire Protection Association Standard for Portable Fire Extinguishers):
Light (Low) Hazard
Light (Low) hazard occupancies shall be classified as locations where the quantity and combustibility of Class A combustibles and Class B flammables are low and fires with relatively low rates of heat release are expected.
Light (Low) hazard occupancies shall be classified as locations where the quantity and combustibility of Class A combustibles and Class B flammables are low and fires with relatively low rates of heat release are expected.
Ordinary (Moderate) Hazard
Ordinary (Moderate) hazard occupancies shall be classified as locations where the quantity and combustibility of Class A combustible materials and Class B flammables is moderate and fires with moderate rates of heat release are expected.
Ordinary (Moderate) hazard occupancies shall be classified as locations where the quantity and combustibility of Class A combustible materials and Class B flammables is moderate and fires with moderate rates of heat release are expected.
Extra (High) Hazard
Extra (High) hazard occupancies shall be classified as locations where the quantity and combustibility of Class A combustible material is high or where high amounts of Class B flammables are present and rapidly developing fires with high rates of heat release are expected
It is important to properly determine the hazard level for all areas. You may be required to install multiple extinguishers or extinguishers with multiple ratings. Restaurants for example, require multiple extinguishers due to multiple hazards. Low hazards in dining areas would require a Class A extinguisher, and high hazards in the kitchen would require a Class K extinguisher.
Extra (High) hazard occupancies shall be classified as locations where the quantity and combustibility of Class A combustible material is high or where high amounts of Class B flammables are present and rapidly developing fires with high rates of heat release are expected
It is important to properly determine the hazard level for all areas. You may be required to install multiple extinguishers or extinguishers with multiple ratings. Restaurants for example, require multiple extinguishers due to multiple hazards. Low hazards in dining areas would require a Class A extinguisher, and high hazards in the kitchen would require a Class K extinguisher.
Special considerations have to be made with Class B fires. There are four typical types of flammable liquid fires:
- Fire involving liquids at least 1/4" deep.
- Spill fires in which the burning liquid is less than 1/4" deep.
- Fires in which the burning liquid or gas is under pressure.
- Three dimensional fires, involving burning liquids that are in motion.
Deep liquid fires build up more heat than spill fires and are best extinguished with agents that smother the fire such as foam. Spill fires can be brought under control with carbon dioxide or dry chemical extinguishers. Gas under pressure can only be controlled with dry chemical. Extinguishers used for fighting pressurized Class B fires must be outfitted with a special nozzle, which allows for the rapid release of more dry chemical. These extinguishers are known as fast flow extinguishers.
- Fire involving liquids at least 1/4" deep.
- Spill fires in which the burning liquid is less than 1/4" deep.
- Fires in which the burning liquid or gas is under pressure.
- Three dimensional fires, involving burning liquids that are in motion.
Deep liquid fires build up more heat than spill fires and are best extinguished with agents that smother the fire such as foam. Spill fires can be brought under control with carbon dioxide or dry chemical extinguishers. Gas under pressure can only be controlled with dry chemical. Extinguishers used for fighting pressurized Class B fires must be outfitted with a special nozzle, which allows for the rapid release of more dry chemical. These extinguishers are known as fast flow extinguishers.
How Many Extinguishers are Required?
There are four topics to review when installing portable fire extinguishers. You must first identify the hazards that are present, and recognize even trace amounts of each fire classification to determine the proper number of extinguishers required. Next, you must determine the size of the fire extinguisher, and establish the quantity of extinguishers needed by the coverage allowed per Local and National fire codes. Last, you must distribute the portable fire extinguishers per the allowable travel distance to each fire extinguisher.
Class A Locations
Criteria | Light (Low) Hazard Occupancy | Ordinary (Moderate) Hazard Occupancy | Extra (High) Hazard Occupancy |
| Minimum Rated single extinguisher | 2-A | 2-A | 4-A |
| Maximum floor area per unit of A | 3,000 ft2 | 1,500 ft2 | 1,000 ft2 |
| Maximum floor area for extinguisher | 11,250 ft2 | 11,250 ft2 | 11,250 ft2 |
| Maximum travel distance to extinguisher | 75 ft | 75 ft | 75 ft |
Source: NFPA 10, 2007 edition Table 6.2.1.1 Fire Extinguisher Size and Placement for Class A Hazards
Class B Locations
Type of Hazard | Basic Minimum Extinguisher Rating | Maximum Travel Distance to Extinguisher |
| 5-B | 30 ft | |
| Light (Low) | 10-B | 50 ft |
| 10-B | 30 ft | |
| Ordinary (Moderate) | 20-B | 50 ft |
| 40-B | 30 ft | |
| Extra (High) | 80-B | 50 ft |
Source: NFPA 10, 2007 edition Table 6.3.1.1 Fire Extinguisher Size and Placement for Class B Hazards
Class C Locations
Class C extinguishers are required where energized electrical equipment is directly involved in or surrounding electrical equipment.
Class D Locations
Class D extinguisher locations shall not be located more than 75 ft. from the hazard. Size determination for Class D locations is based on the specific combustible metal, particle size, area to be covered, and manufacturer recommendations.
Class K Locations
Class K hazards shall have a fire extinguisher located where there is a potential for a fire involving combustible cooking media (vegetable or animal oils and fats). The extinguisher shall be located no more than 30 ft. from the hazard.
NFPA 10 requires you to maintain your fire protection equipment in good working order and maintain inspection,
testing and maintenance records. Inspections will be performed on an Annual basis.
testing and maintenance records. Inspections will be performed on an Annual basis.
EXAMPLES OF WORK PERFORMED DURING AN INSPECTION INCLUDE:
- Check that unit is properly hung with the proper manufacturer’s hanger.
- Check the gauge pressure.
- Check the condition of the gauge and its compatibility with the extinguisher.
- Check the weight of the extinguisher.
- Check that the last hydrostatic test date is within code requirements.
- Check the last 6−year maintenance inspection date if applicable.
- Check the valve and shell for damage or corrosion.
- Remove the hose and inspect it for cracks or splits.
- Check the hose threads for signs of wear.
- Check the condition of the discharge horn.
- Check for obstructions that interfere with accessibility of the unit.
- Break the extinguisher seal and remove the locking pin.
- Replace the locking pin and reseal the extinguisher.
- Check the valve opening for powder or any foreign matter.
- For dry extinguishers, fluff the powder by turning the unit.
- Check the condition of the hose/horn retention band at the side of the extinguisher.
- Check that the unit’s classification is properly identified with the appropriate decal/signage.
- Check that the operating instructions are clean and legible.
- Check that the unit is properly located within the normal path of travel, at the required height.
- Check that the unit is visible, unobstructed and in proper location.
- Compile a complete location report, explaining any deficiencies.
- Recommend corrective action to be taken in accordance with recognized codes for care and maintenance.
- Upon completion of inspection and any necessary repairs, applicable inspection documents and noted deficiencies shall be left at location and available electronically.
- Tag all portable fire extinguishers as required and perform required record keeping.
Extinguisher Type | Test Interval (years) |
| Stored-pressure water, water mist, loaded stream, and/or anti-freeze | 1 |
| Pump tank water and pump tank calcium chloride base | 1 |
| Dry chemical, cartridge and cylinder operated, with mild steel shells | 1 |
| Dry powder, cartridge and cylinder operated, with mild steel shells | 1 |
| Wetting agent | 1 |
| Stored pressure water | 5 |
| Stored-pressure dry chemical, with stainless steel shells | |
| Carbon dioxide | 5 |
| Wet chemical | 5 |
| Dry chemical stored-pressure, with mild steel shells, brazed brass shells, and aluminum shells | 5 |
| Halogenated agents | 6 |
| Dry powder, stored pressure, with mild steel shells | 6 |
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