OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

September 9, 1991

Mr. Glen B. White
Scientific Information Services
4820 Highway, 377 South
Post Office Box 122075
Fort Worth, Texas 76116

Dear Mr. White:

This is in further response to your letter of July 20, concerning the storage of flammable and/or combustible materials in fiberglass reinforced plastic (FRP) tanks.

You referenced the Occupational Safety and Health Administration (OSHA) standard at 1910.106(b)(1)(i)(a) with respect to the definition of "noncombustible construction" of storage tanks. You inquired if FRP containers that are designed for underground storage of flammable and/or combustible materials could be used for aboveground and indoor storage.

OSHA defines noncombustible materials as those materials which are not capable of burning or igniting. Since FRP is capable of burning in the presence of a flame, OSHA considers such material to be combustible, and usage of such material in constructing storage tanks for flammable or combustible liquids to be located aboveground or inside buildings will be in violation of 1910.106(b)(1)(i)(b).

The exemption provided in 1910.106(b)(1)(iii)(b) for tanks designed for underground service with capacities less than 2500 gallons, which are allowed to be used for aboveground service, does not apply to tanks that are built of combustible materials.

Thank you for your interest in safety and health of employees. If we may be of further assistance, please contact us.


Gerard F. Scannell
Assistant Secretary