ages the use of the hoods for transferring such materials.)

  • Use chemical storage refrigerators only for storing chemicals.

  • Label these refrigerators with the following signage:


  • Seal containers to minimize escape of corrosive, flammable, or toxic vapors.

  • Label all materials in the refrigerator with contents, owner, date of acquisition or preparation, and nature of any potential hazard.

  • Do not store flammable liquids in a refrigerator unless it is approved for such storage. Such refrigerators are designed not to spark inside the refrigerator. If refrigerated storage is needed inside a flammable-storage room, it is advisable to choose an explosion-proof refrigerator.

4.E.3 Storing Flammable and Combustible Liquids

The National Fire Protection Association (NFPA) Standard 45 (NFPA, 1991d) limits the quantity of flammable and combustible liquids per 100 square feet of laboratory space. (Local regulations should also be consulted.) The quantity depends on these safety factors:

  • construction of the laboratory,

  • fire protection systems built into the laboratory,

  • storage of flammable liquids in flammable liquid storage cabinets or safety cans, and

  • type of laboratory (i.e., instructional or research and development).

Many laboratories have a B (business) classification with sprinkler systems and have a flammable and combustible liquid storage limitation, as shown in Table 4.2.

The container size for storing flammable and combustible liquids is limited both by NFPA Standards 30 and 45 and by OSHA. Limitations are based on the type of container and the flammability of the liquid, as shown in Table 4.3.

The following precautions should be taken when storing flammable liquids:

  • When possible, store quantities of flammable liquids greater than 1 L (approximately 1 quart, or 32 ounces) in safety cans. Refer to Table 4.3.

  • Store combustible liquids either in their original (or other NFPA-and DOT-approved) containers or in safety cans. Refer to Table 4.3.

4.E.4 Storing Gas Cylinders

The following precautions should be taken when storing compressed gas cylinders:

  • Always label cylinders so you know their contents; do not depend on the manufacturer's color code.

  • Securely strap or chain gas cylinders to a wall or bench top. In seismically active areas, it may be advisable to use more than one strap or chain.

  • When cylinders are no longer in use, shut the valves, relieve the pressure in the gas regulators, remove the regulators, and cap the cylinders.

  • Segregate gas cylinder storage from the storage of other chemicals.

  • Keep incompatible classes of gases stored separately. Keep flammables from reactives, which include oxidizers and corrosives.

  • Segregate empty cylinders from full cylinders.

  • Keep in mind the physical state—compressed, cryogenic, and/or liquefied—of the gases.

  • Warning: Do not abandon cylinders in the dock storage

TABLE 4.2 Storage Limits for Flammable and Combustible Liquids for Laboratories: B Classification with Sprinkler System

Class of Liquid

Flash Point (oC)

Amount (gallons per 100 square feet)

Class I Flammable

Below 38


Class II Combustible



Class IIIA Combustible



Class IIIB Combustible

Above 93


NOTE: Liquid (pumpable) flammable waste is included in the storage limitation. Non-pumpable waste is not included. Locations with an H (hazard) classification have much higher limits. Inside storage rooms for flammable liquids, the limits are from 5 to 10 gallons per square foot, depending on the size and construction of the room.

SOURCE: NFPA (1991c), Chapter 2-2, "Laboratory Unit Fire Hazard Classification."

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