OSHA 29CFR 1910.110(b)(11)(iv):
Direct gas-fired tank heaters shall be constructed and installed as follows:
A. Direct gas-fired tank heaters, and tanks to which they are applied, shall only be installed above ground.
B. Tank heaters shall be permanently marked with the name of the manufacturer, the rated B.t.u. input to the burner, and the maximum vaporizing capacity in gallons per hour.
C. Tank heaters may be an integral part of a fuel storage container directly connected to the container liquid section, or vapor section, or both.
D. Tank heaters shall be provided with a means for manually turning off the gas to the main burner and pilot.
E. Tank heaters shall be equipped with an automatic safety device to shut off the flow of gas to main burners, if the pilot light should fail. When flow through pilot exceeds 2,000 B.t.u. per hour, the pilot also shall be equipped with an automatic safety device to shut off the flow of gas to the pilot should the pilot flame be extinguished.
F. Pressure regulating and pressure reducing equipment if located within 10 feet of a direct fired tank heater shall be separated from the open flame by a substantially airtight noncombustible partition.
G. The following minimum distances shall be maintained between a storage tank heated by a direct fired tank heater and the nearest important building or group of buildings:
• Ten feet for storage containers of less than 500 gallons water capacity.
• Twenty-five feet for storage containers of 500 to 1,200 gallons water capacity.
• Fifty feet for storage containers of over 1,200 gallons water capacity.
H. No direct fired tank heater shall raise the product pressure within the storage container over 75 percent of the pressure set out in the second column of Table H-31. [Table H-31 reproduced below]
(1) New storage containers of the 80 type have not been authorized since Dec. 31, 1947.
(2) Container type may be increased by increments of 25. The minimum design pressure of containers shall be 100% of the container type designation when constructed under 1949 or earlier editions of the ASME Code (Par. U-68 and U-69). The minimum design pressure of containers shall be 125% of the container type designation when constructed under:
1. the 1949 ASME Code (Par.U-200 and U-201),
2. 1950, 1952, 1956, 1959, 1962, 1965, and 1968 (Division 1) editions of the ASME Code, and
3. all editions of the API-ASME Code.
(3) Construction of containers under the API-ASME Code is not authorized after July 1, 1961.
OSHA 29 CFR 1910.110(b)(20)(iii):
Unattended heaters used inside buildings for the purpose of animal or poultry production or care shall be equipped with an approved automatic device designed to shut off the flow of gas to the main burners, and pilot if used, in the event of flame extinguishment.
OSHA 29 CFR 1910.110(c)(5)(i)(h):
Portable heaters, including salamanders, shall be equipped with an approved automatic device to shut off the flow of gas to the main burner, and pilot if used, in the event of flame extinguishment. Such heaters having inputs above 50,000 B.t.u. manufactured on or after May 17, 1967, and such heaters having inputs above 100,000 B.t.u. manufactured before May 17, 1967, shall be equipped with either.