Understanding flammable liquid storage cabinets
NFPA Journal, March/April 2011
Flammable and combustible liquids are used in most buildings. In some industrial operations, a lot of these liquids are used, while in other occupancies, the quantities may be small. Nonetheless, the basic rules for the safe handling of these liquids are the same. NFPA 101®, Life Safety Code®, as well as NFPA 5000®, Building Construction and Safety Code®, and NFPA 1, Uniform Fire Code, all reference NFPA 30, Flammable and Combustible Liquids Code. In addition, OSHA General Industry Standards 1910.106, "Flammable & Combustible Liquids," was based on, and copied from, an earlier edition of NFPA 30.
Flammable liquid storage cabinets are commonly used in buildings to store incidental flammable and combustible liquids. The primary purpose of these cabinets is to promote good housekeeping and provide minimal separation of the liquids in the cabinet from a small exposing fire. Listed cabinets are tested to limit the internal temperature in the cabinet to 325oF (163oC) for a 10-minute fire test.
The 2008 edition of NFPA 30 addresses the use of flammable liquid storage cabinets in Section 9.5. Cabinets can store up to 120 gallons (454 liters) of liquid per cabinet and are not required to be vented, though manufacturers generally provide vent openings. In fact, the code states in Paragraph 126.96.36.199 that the bung caps sealing the vents should be kept securely in place. Why then do manufacturers provide the vents?
One reason is that some stored materials, such as pharmaceuticals, can release toxic vapors that may be harmful for cabinet users. In this case, it may be beneficial to vent the cabinets to reduce exposure to these vapors. If the cabinets are vented, they must be vented to the exterior of the building, and the vent piping must maintain the integrity of the vents. Generally, this will require metallic vent piping.
Earlier editions of NFPA 30 limited the number of cabinets in a given fire area. However, the 2008 edition of the code introduced the concept of "control areas." A control area is a room, space, floor, or entire building in which the quantity of liquids used, dispensed, or stored does not exceed the limits established in the code. These limits are called "maximum allowable quantities," or MAQs.
Table 9.6.1 of NFPA 30 specifies the MAQ permitted in a control area. MAQs may be increased if the liquids are stored in cabinets or safety cans and if automatic sprinklers are provided. However, MAQs are reduced as the liquids are located on higher floors of the building. Table 9.7.2 specifies the percent reduction of MAQ as the liquid storage areas are located on higher floors. In addition, the number of control areas per floor drops when liquids are stored on higher floors.
While the number of flammable liquid storage cabinets is not limited, the total quantity of liquid storage MAQs per control area is. If a facility must have more flammable or combustible liquids than permitted by the code for a control area, it is considered a Protection Level 2 or 3 facility, as specified in Section 9.8. Additional safeguards are required for Protection Level 2 and 3 spaces.
The use of flammable liquid storage cabinets is certainly a good way to isolate and safely store flammable and combustible liquids. The quantity of liquids that can be located outside of storage cabinets or storage rooms will be discussed in a later column.
Chip Carson, P.E., is president of Carson Associates, Inc., a fire engineering and code consultancy. He is a former member of NFPA's Board of Directors.