Flammable Storage Cabinets

7/17/2017

Every time I am tasked to perform a Safety and Health audit; whether it’s for one of a project or as an independent reviewer, it seems that there is considerable frustration out there regarding the requirements for storing and/or using flammable liquids.  To prevent fires, the National Fire Protection Association (NFPA) and the International Code Council (ICC) have developed guidelines for the safe storage and use of flammables under the Uniform Fire Code. While these practices are guidelines and are not, by themselves, regulatory requirements, they can be mandatory when a federal, state or local authority chooses to adopt them. And as it turns out, OSHA has adopted many of these guidelines and are specified in the following regulations:

• General industry (29 CFR 1910.106)
• Construction industry (29 CFR 1926.152)
• Shipyard industry (29 CFR 1915.36)

In addition to these regulations, OSHA’s new Hazard Communication Standard, the definition of what a flammable liquid has been revised. According to this regulation, a flammable liquid is any liquid having a flashpoint at or below 199.4°F (93 °C) and are divided into four categories:

• Category 1: Liquids with flashpoints below 73.4°F (23°C) and boiling points at or below 95°F (35°C) (1910.106(a)(19)(i)). Examples: acetaldehyde and ethyl ether.
• Category 2: Liquids with flashpoints below 73.4°F (23°C) and boiling points at or above 95°F (35°C) (1910.106(a)(19)(ii)). Examples: acetone, benzene and toluene.
• Category 3: Liquids with flashpoints at or above 73.4°F (23°C) and at or below 140°F (60°C). When a Category 3 liquid with a flashpoint at or above 100°F (37.8°C) is heated for use to within 30°F (16.7°C) of its flashpoint, it must be handled in accordance with the requirements for a Category 3 liquid with a flashpoint below 100°F (37.8 °C) (1910.106(a)(19)(iii)).
• Category 4: Liquids having flashpoints above 140°F (60°C) and at or below 199.4°F (93°C). When a Category 4 flammable liquid is heated for use to within 30°F (16.7°C) of its flashpoint, it must be handled in accordance with the requirements for a Category 3 liquid with a flashpoint at or above 100°F (37.8°C) (1910.106(a)(19)(iv)). When a liquid with a flashpoint greater than 199.4 °F (93 °C) is heated for use to within 30 °F (16.7 °C) of its flashpoint, it must be handled in accordance with the requirements for a Category 4 flammable liquid (1910.106(a)(19)(v)).

Whether liquids are Category 1 or 4 is not the only factor you should consider when determining safe storage needs. You also need to consider ignition temperature, lower and upper explosive limits (LEL or UEL), vapor pressure, and specific gravity and vapor density when storing these materials.

The NFPA, OSHA and Uniform Fire Code (UFC) require flammable cabinets to be designed and constructed to specific provisions. Storage cabinets must be designed and constructed to limit the internal temperature to not more than 325°F when subjected to a 10-minute fire test and the cabinets must be labeled in conspicuous lettering, “Flammable – Keep Fire Away.” OSHA also specifies that metal cabinets must be constructed in the following manner:

• Bottom, top and sides of cabinet must be at least No. 18-gauge sheet iron
• Cabinet must be double walled with one and one-half inch airspace
• Joints must be riveted, welded or made tight by some equally effective means
• Door must have a three-point latch
• Door-sill must be raised at least two inches above the cabinet bottom to retain spilled liquid within the cabinet

OSHA also provides an option for wood cabinets which must be constructed in the following manner:

• Bottom, top and sides of cabinet must be constructed of exterior-grade plywood at least one inch thick
• Plywood must not break down or delaminate under fire conditions
• Joints shall be rebutted and fastened in two directions with flathead wood screws
• When more than one door is used, they must have a rebutted overlap of not less than one inch
• Hinges must be mounted in such a manner as not to lose their holding capacity due to loosening or burning out of the screws when subjected to the fire test

OSHA limits the quantity of liquids that may be kept outside of an inside storage room or storage cabinet in a building or in any one fire area of a building. These limits are only applicable to those portions of an industrial plant where the use and handling of flammables is only incidental to the principal business. The quantity of liquid that may be stored outside of a storage room or storage cabinet in a building or in any one fire area of a building cannot exceed:

• 25 gallons of Category 1 liquids in containers
• 120 gallons of Category 2, 3 or 4 liquids in containers
• 660 gallons of Category 2, 3 or 4 liquids in a single portable tank

The amount of flammable liquid storage and location of cabinets are also regulated, stipulating that not more than 60 gallons of Category 1, 2 or 3 flammable liquids, nor more than 120 gallons of Category 4 flammable liquids may be stored in a storage cabinet. Also, according to NFPA, not more than three such cabinets may be located in a single fire area.

Both OSHA and NFPA define a fire area as, “An area of a building separated from the remainder of the building by construction having a fire resistance of at least one hour and having all communicating openings properly protected by an assembly having a fire resistance rating of at least one hour.”

As one might expect, the rules of using flammables are quite extensive and go beyond storage requirements. However, by properly storing these materials, we have addressed a fundamental concern.  Regulations for flammable safety cans, and proper distances from non-compatibles are also important to consider. Questions regarding storage/use of flammables can be best answered by your S&H professional. If he/she does not have an immediate answer, without a doubt, they will be able to find the answer in a timely manner.   

If there must be trouble, let it be in my day, that my child may have peace – Thomas Paine