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Storing Flammable and Combustible Liquids
Comply With 29 CFR 1910.106

Due to the increased use of non-water-based chemicals, the potential exposure to the hazards associated with these chemicals has also increased, including hazards to worker's health and property. Flammability poses one of the most dangerous potential hazards when dealing with the storage, handling and use of chemicals, warranting special precautions be taken in handling and storing hazardous liquids to prevent the risk of fires.

The Occupational Safety and Health Administration (OSHA) has developed regulations, based on the National Fire Protection Agency's standard on flammable and combustible liquids (NFPA 30), governing the storage and use of flammable and combustible liquids for General Industry (29 CFR 1910.106) to define how employers can minimize employee exposure or injury.

Note: OSHA regs for: Construction Industry (29 CFR 1926.152) and Shipyard Industry (29 CFR 1915.36)

FLAMMABLES:
According to the regulations, flammable liquids are defined as those with flashpoints below 100º F and combustible liquids as those that have flashpoints at or above 100º F.

Class IA

Liquids having flashpoints below 73° F (22.8° C) and having boiling points below 100°F (37.8°C), such as Acetaldehyde, ethyl ether and cyclohexane.

Class IB

Liquids having flashpoints below 73° F (22.8° C) and having boiling points at or above 100° F (37.8°C) , such as Acetone, benzene and toluene.

Class IC

Liquids having flashpoints at or above 73° F (22.8° C) and having boiling points below 100° F (37.8°C), such as Hydrazine, styrene and turpentine.

COMBUSTIBLES:

29 CFR 1910.106(a)(18) defines a combustible liquid as any liquid having a flashpoint at or above 100° F (37.8° C) . Combustible liquids are divided into two classes:

Class II

Liquids having flashpoints at or above 100° F (37.8° C) and below 140° F (60° C), such as Acetic acid, naptha and stoddard solvent.

Class III

Liquids having flashpoints at or above 140°F (60°C). Class III liquids are subdivided into two subclasses:

    Class IIIA

    Liquids having flashpoints at or above 140°F (60°C) and below 200°F, such as Cyclohexanol, formic acid and nitrobenzene.

    Class IIIB

    Liquids having flashpoints at or above 200°F (93.3°C), such as Formalin and picric acid.


Class IIIB liquids include those with flashpoints at or above 200°F (93.3°C). This section does not cover Class IIIB liquids. Where the term "Class III liquids" is used in the section, it shall mean only Class IIIA liquids. (Class IIIB is used in this document for reference purposes only.)

*Note: When a combustible liquid is heated for use to within 30°F (16.7°C) of its flashpoint, it shall be handled in accordance with the requirements for the next lower class of liquids (1910.106(a)(18)(iii)).

The flashpoint and boiling point determine the class of a liquid. Though it is not the only criteria used to determine the hazards of a liquid, other factors such as ignitions temperature, explosive limits (LEL or UEL), vapor pressure, specific gravity and vapor density should also be considered for the proper use and storage of hazardous liquids.

Safety Cans
OSHA defines a safety can as ". . . An approved container, of not more than 5 gallons capacity, having a spring-closing lid and spout cover and so designed that it will safely relieve internal pressure when subjected to fire exposure" (1910.106(a)(29)). The use of safety cans helps reduce the hazards associated with flammable and combustible liquids.

Safety cans that hold flammables must comply with the requirements listed in 29 CFR 1910.106(d)(2) . Safety cans are widely used because they are self-closing and properly vented.

Note: Many local laws and insurance carriers require safety cans to be Factory Mutual (FM) or Underwriter Laboratory (UL) approved. FM and UL are nationally recognized independent testing laboratories to which manufacturers submit products for evaluation of their ability to meet safety requirements under intended use. Products that meet the requirements are given either a FM or UL product approval. Both laboratories are also recognized by OSHA.

In addition to the storage of flammable and combustible liquids in safety containers, 29 CFR 1910.106 limits the amount of liquid in a single container. The chart below shows the allowable amounts of liquid are for each class of liquid.

MAXIMUM ALLOWABLE SIZE OF CONTAINERS AND METAL PORTABLE TANKS
Container Type
Flammable Liquids
Combustible Liquids
Class IA
Class IB
Class IC
Class II
Class III
Glass or approved plastic
1 pt.
1 qt.
1 gal.
1 gal.
1 gal.
Metal (other than DOT drums)
1 gal.
5 gal.
5 gal.
5 gal.
5 gal.
Safety Cans
2 gal.
5 gal.
5 gal.
5 gal.
5 gal.
Metal Drum (DOT spec.)
60 gal.
60 gal.
60 gal.
60 gal.
60 gal.
Approved Metal Portable Tanks
660 gal.
660 gal.
660 gal.
660 gal.
660.gal

There are exceptions to this rule:

  • Medicines, beverages, foodstuffs, cosmetics, and other common consumer products, when packaged according to commonly accepted practices.

29 CFR 1910.106 also limits the total amount of a liquid kept outside of a cabinet or storage room. The quantity of liquid that may be stored outside of an inside storage room or a cabinet in any one fire area of a building cannot exceed:
  • 25 gallons of Class IA liquids in containers
  • 120 gallons of Class IB, IC, II or III liquids in containers
  • 660 gallons of Class IB, IC, II or III liquids in a single portable tank
The amount of liquid storage and location of cabinets is regulated. 1910.106 (d)(3) states, "Not more than 60 gallons of Class I or Class II liquids, nor more than 120 gallons of Class III liquids may be stored in a storage cabinet." Also, according to NFPA 304.3.2, not more than three (3) such cabinets may be located in a single fire area.

Flammable Storage Cabinet Requirements

The NFPA, OSHA and UFC require flammable cabinets to be designed and constructed to specific requirements. 1910.106(d)(3)(ii)(a) dictates that metal cabinet be constructed with the following specifications:
  • Bottom, top and sides of cabinet shall be at least No. 18 gauge sheet steel
  • Cabinet must be doubled walled with 1½" airspace
  • Joints shall be riveted, welded or made tight by some equally effective means
  • Door shall have a three point latch
  • Door sill shall be raised at least 2" above the cabinet bottom to retain spilled liquid within the cabinet
  • Cabinet shall have a "FLAMMABLE—KEEP FIRE AWAY" legend
Fire Areas
OSHA does not provide a definition of a fire area in this standard. However, a fire area is defined by NFPA Code 30 as, "An area of a building separated from the remainder of the building by construction having a fire resistance of at least 1 hour and having all communicating openings properly protected by an assembly having a fire resistance rating of at least 1 hour." The NFPA also provides a special provision for the grouping of flammable cabinets in an industrial facility. Because most industrial settings do not have walls or barriers within a facility, "In an industrial occupancy, additional cabinets may be located in the same fire area if the additional cabinets, or the group of not more than three (3) cabinets, is separated from the other cabinets or group of cabinets by at least 100 feet (30 m)."

Sources for More Information
National Fire Protection Association, Flammable and Combustible Liquids Code Handbook, Fourth edition, ed. Robert Benedetti, 1991.

United States Office of the Federal Register National Archives and Records Administration, 29 Code of Federal Regulations Parts 1900 to 1910, (Washington: GPO 1994).

National Institute of Occupational Safety & Health, Pocket Guide to Chemical Hazards, U.S. Department of Health and Human Services. (Washington: GPO 1994).

Questions & Answers

Q. When dispensing flammable liquids, do I have to use bonding and grounding wires?

A. Only Class I liquids are required to be bonded and grounded, according to 1910.106(e)(6)(ii). However, for your own safety, bonding and grounding should always be used when dispensing flammable or combustible liquids.

Q. Am I required to have a flammable storage cabinet?

A. OSHA does not require the use of flammable storage cabinets unless the total amount of flammable and/or combustible liquids reaches a given amount. Local authorities and insurance companies may require the use of flammable storage cabinets in quantities less than that of OSHA.

Q. What is the difference between type I and type II safety cans?

A. A Type I safety can has one spout for both pouring and filling. A Type II safety can has two openings; one for pouring and one for filling.

Q. What is a flame arrestor, and what purpose does it serve?

A. A flame arrestor is a mesh or perforated metal insert within a flammable storage container (safety can, cabinet) which protects its contents from external flames or ignition. It also dissipates heat. All Type I, Type II, disposal and specialty cans include a flame arrestor.

Q. Are flammable cabinets required to have mechanical ventilation?

A. OSHA does not normally require the use of mechanical ventilation. The NFPA recommends that cabinets not be mechanically ventilated, but if they are, they should be ventilated in accordance to NFPA 91 Exhaust Systems for Air Conveying of Materials.
Please Note: The information contained in this publication is intended for general information purposes only. This publication is not a substitute for review of the applicable government regulations and standards, and should not be construed as legal advice or opinion. Readers with specific questions should refer to the cited regulation or consult with an attorney.


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