OSHA’s Flammable & Combustible Liquids

Each year, fires destroy many places of business and homes because flammable and combustible liquids are not properly stored. Take some time to look around your place of employment or your home to ensure that these potential hazards are eliminated. Take the time to know what flammable liquids you’re working with and what the necessary precautions are. Remember flashpoints, auto ignition temperatures, and the basic principles of air and vapor mixtures.

When a flammable liquid is within the explosive range, you need to take extra precautions and follow the rules. Flammable liquids are used in hundreds of thousands of processes, and they’re used safely every day. However, the potential for mishaps is always there. Someone forgets to do this, or that, or some procedure is violated.

The answer to flammable liquid safety is to follow company safety procedures and work rules and, of course, the information provided by the manufacturer. Each employee holds the key to safety when working with flammable liquids. Knowledge is the first step, but putting that information to work for you makes the difference in safety.

Proper flammable material storage is essential for fire prevention. Flammable storage locations can range from purpose-built buildings or storerooms to NFPA-rated flammable storage cabinets. All flammable storage cabinets must be vented to the outside when they are installed. OSHA regulations for this hazard can be found in 29 CFR 1910.101 to 1910.126 and can be read online at www.osha.gov.

Here are some answers to basic questions that are usually asked when I teach at the OSHA Training Institutes:

Q: Why store flammable and combustible liquids inside a flammable liquid storage cabinet?
A: To protect flammable liquids against flash fire, to prevent the containers from building excessive internal pressure, and to contain spilled flammable liquids that can further spread fire. The picture below demonstrates how flammable storage cabinets effectively protect the contents inside from fire. Fire burned the exterior of the storage cabinet; flammable solvents inside were protected from the fire.

Q: Is my existing flammable liquid storage cabinet acceptable?
A: Cabinets must be Underwriter Laboratories (U.L.) (1275) listed or Factory Mutual (F.M.) approved, which is indicated by a permanent manufacturer’s label on the cabinet. Alternatively, cabinets must be constructed in accordance with the following:

■ Unlisted metal cabinets shall be of steel having a thickness of not less than 0.044 (1.12mm) (18 gauge). The cabinet, including the door, shall be double-walled with 1-1/2" (38.1mm) airspace between the walls. Joints shall be riveted or welded and shall be tight-fitting. Doors shall be well-fitted, self-closing, and equipped with a latching device.

■ Unlisted wooden cabinets, including doors, shall be constructed of not less than 1" (25.4mm) exterior grade plywood. Joints shall be rabbited and shall be fastened in two directions with wood screws. Door hinges shall be of steel or brass. The cabinet shall be painted with an intumescent-type paint. Doors shall be well-fitted, self-closing, and equipped with a three-point latch.

Regardless of whether it is a wood or metal cabinet, each cabinet shall have the following:

■ The bottom of the cabinet shall be liquid-tight to a height of at least 2" (50.8mm).
■ The door shall be well-fitted, self-closing, and equipped with a three-point latch.
■ A conspicuous label on a contrasting background which reads, “FLAMMABLE – KEEP FIRE AWAY” on the front.

Q: What is the maximum quantity of flammable and combustible liquids that I can store inside a single storage cabinet?
A: Cabinets are available in different sizes, ranging from 4-gallon (15-liter) to 120-gallon (454-liter) capacity. However, per regulations, no more than 60 gallons of Class I-A flammable liquids may be stored inside a single cabinet. Class I-A flammable liquid is a liquid having a closed cup flash point below 73°F (22.8°C) and boiling point below 100°F (37.8°C).

Q: Should the flammable liquid storage cabinet be vented?
A: When used for the storage of closed containers, a flammable liquid storage cabinet is not required to be vented for fire protection purposes. Vent openings must be sealed with the bungs supplied with the cabinet or with bungs specified by the cabinet manufacturer.

If venting is required for other reasons, such as personnel exposure or dispensing operations within the cabinet, then venting using the opening provided by the manufacturer shall be provided with a metallic vent pipe directly to the outdoors or to the fume hood exhaust duct in a manner that is acceptable to the local Fire Department.

Proper venting practices:

■ Remove steel bungs from the factory-furnished vent ports
■ Connect the metal vent pipe directly to the lower vent port since hydrocarbon vapors are usually heavier than air
■ Inspect the upper vent port to ensure the flame arrestor is installed
■ The upper vent port with the flame arrestor will provide make-up air for efficient purging
■ DO NOT CUT OR DRILL INTO THE EXTERIOR OF THE CABINET FOR VENT CONNECTION

Q: Should the flammable liquid storage cabinet be grounded?
A: No, unless you are dispensing from one of the containers when it is sitting inside the cabinet.

Q: Who makes flammable liquid storage cabinets, and where can I purchase one?
A: Cabinets can be purchased from lab equipment supply companies or safety equipment supply companies.

Should you have any questions concerning this topic, please write to me at jpodojil@podojilconsulting.com, and I will respond to them on your behalf.

A special thank you to OSHA and to the University of California, Berkeley, for permission to use some of their information from their fact sheet.