Flammable Liquids Storage

Both flammable and combustible liquids, excluding those subject to incidental use, must be stored in flammables cabinets. Other materials as well should


Both flammable and combustible liquids, excluding those subject to incidental use, must be stored in flammables cabinets. Other materials as well should be stored in specialty cabinets separate from flammable liquids. A listing follows of classes of chemicals that require storage apart from flammable liquids.


  • Acids should be stored together. Sulfuric acid (H2SO4) and hydrochloric acid (HCl) should be segregated from other acids, as well as from each other, unless their containers are completely enclosed in an unbreakable receptacle.

  • Bases should be stored together. Flammable bases should be segregated from other bases, as well as from each other.

  • A total of one gallon of nonstored acids and one gallon of nonstored bases is permitted in a single room, provided all containers have a total capacity of less than one gallon and are unbreakable.

  • Cabinet requirements. Cabinets or other storage containers must be designed and rated by the manufacturer for use with corrosives. Flammable corrosives must be stored in a cabinet rated for both corrosives storage and flammable storage.

Although oxidizers, flammable oxidizers, pyrophorics, organic peroxides, explosive materials and water-reactive materials also have separate and specific storage requirements, these are not discussed here, since they are not normally used by concrete producers. For the sake of further simplicity, storage of liquids, as opposed to flammable combustible solids and gasses, will be considered.

Both flammable and combustible liquids can be stored together. By definition, a flammable liquid has a flash point of 100_F or less. OSHA 29 CFR 1910.106(a)(19) states:

Any liquid having a flash point below 100_F (37.8_C), except any mixture having components with flash points of 100_F (37.8_C) or higher, the total of which make up 99 percent or more of the total volume of the mixture. Flammable liquids shall be known as Class I liquids.

By contrast, a combustible material has a flashpoint above 100_F, which makes it somewhat harder to ignite. OSHA defines a combustible liquid as:

Any liquid having a flash point at or above 100_F (37.8_C), but below 200_F (93.3_C), except any mixture having components with flashpoints of 200_F (93.3_C), or higher, the total volume of which make up 99 percent or more of the total volume of the mixture.

A flash point of 100?F does not indicate that the material will catch fire at that temperature, but it will start to evaporate into the air; and, the airborne vapor is flammable if ignited. The actual definition for flash point is the lowest temperature at which a liquid can form an ignitable mixture in air near the surface of the liquid.

Accordingly, the lower the flash point, the easier it is to ignite the material. The flash point can be indicated on the container the material is stored in, or it can be identified on the Material Safety Data Sheet.

An easy way to remember the difference between flammable and combustible is that all flammable liquids are Class I, while all combustible liquids are Class II and III. Class IIIB combustible liquids Û not regulated by OSHA Û fall in the murky category between combustible and nonflammable, except in conditions that would heat the material above 200_F.

When use and handling of flammable or combustible liquids is incidental, the quantity of liquid that may be located outside a storage room or cabinet inside a building or in any fire area of a building shall not 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 1B, 1C, II, or III liquids in a single portable tank.

As a flammables cabinet cannot adequately be constructed by the average producer, purchasing an approved flammables cabinet is essential. The structure must meet the specifications of Standard Methods of Fire Tests of Building Construction and Materials, NFPA 251-1969, since the standard is incorporated by reference in OSHA 1910.6.

An approved flammables cabinet also will be equipped with appropriately sized perforated vents on two sides, allowing a slow movement of air through the unit. Vents are designed to help minimize the buildup of flammable vapors internally, yet still choke a fire should one occur inside the cabinet. Further, the structure should be grounded to help prevent a static spark from occurring upon opening the cabinet.

According to regulation, at least one portable fire extinguisher of a rating not less than 12-B units shall be located outside of, but not more than 10 feet from, the door opening into any room used for storage. Additionally, at least one portable fire extinguisher of a rating not less than 12-B units must be located not less than 10 feet, nor more than 25 feet, from any Class I or Class II liquid storage area located outside a storage room, but inside a building. And, of course, the cabinet or immediate area should be labeled Danger, Flammable Liquids Storage, No Open Flames nor Smoking.

What determines the size of cabinets is its allowable storage capacity. A cabinet can store a maximum of 60 gallons of Class I or Class II liquids, or 120 gallons of Class III liquids.

Should a producer decide to classify an entire room as storage space, numerous requirements for a flammable and chemical liquids storage room must be met, including construction that complies with test specifications included in NFPA 251-1969. The standard includes special seepage controls, spill controls, special requirements for wiring, ventilation, egress, storage, and fire control. Our advice is to keep it simple: stick with concrete production and purchase commercially approved storage cabinets.

Flammables storage cabinets should be positioned to avoid possible contact with crane loads, vehicles, or forklifts. These cabinets have a way of being easily damaged so that their doors will not close. The high expense of the units coupled with their peculiar double-walled, tight-fitting construction tends to keep damaged cabinets in service even while unrepairable.


Flammable Class IA FP < 73_F
BP < 100_F
Class IB FP < 73_F
BP > 100_F
Class IC FP 73_F
to 100_F
Combustible Class II FP 100_F
to 140_F
Class IIIA FP 140_F
to 200_F
Class IIIB FP above 200_F