46 C.F.R. § 52.01-35
Auxiliary, donkey, fired thermal fluid heater, and heating boilers
(a) To determine the appropriate part of the regulations where requirements for miscellaneous boiler types, such as donkey, fired thermal fluid heater, heating boiler, etc., may be found, refer to table 1 to § 54.01-5 of this subchapter.
(b) Fired vessels in which steam is generated at pressures exceeding 103 kPa gage (15 psig) must meet the requirements of this part.