Section 54.20-2 - Fabrication for hazardous materials (replaces UW-2(a))(a) Pressure vessels containing hazardous materials as defined in § 150.115 of this subchapter must be of the class and construction required by subchapters D, I, or O of this chapter, or, when not specified, of a class determined by the Commandant.(b) Class III pressure vessels must not be used for the storage or stowage of hazardous materials unless there is specific authorization in subchapters D, I, or O of this chapter.CGD 77-147, 47 FR 21810, May 20, 1982