Section 173.335 - Chemical under pressure n.o.s(a)General requirements. A cylinder filled with a chemical under pressure must be offered for transportation in accordance with the requirements of this section and § 173.301 (except for the cylinder valve cap requirements in §§ 173.301(a)(11) and (12) ). In addition, a DOT specification cylinder must meet the requirements in §§ 173.301a , 173.302 , 173.302a , and 173.305 , as applicable. UN pressure receptacles must meet the requirements in §§ 173.301b , 173.302b , and 173.304b , as applicable. Where more than one section applies to a cylinder, the most restrictive requirements must be followed.(b)Filling limits. Cylinders must be filled so that at 50 °C (122 °F) the non-gaseous phase does not exceed 95% of their water capacity and they are not completely filled at 60 °C (140 °F). When filled, the internal pressure at 65 °C (149 °F) must not exceed the test pressure of the cylinder. The vapor pressures and volumetric expansion of all substances in the cylinders must be taken into account.(c)Minimum service pressure. The minimum service pressure must be in accordance with the design specifications of part 178 of this subchapter for the propellant. In any case the minimum test pressure must not be less than 20 bar.(d)Periodic inspection.(1) Except as specified in (d)(2) of this section, the maximum requalification test period for cylinders transporting chemical under pressure n.o.s. is 5 years.(2) For cylinders with maximum capacity of 450 L or less and filled with materials used as fire extinguishing agents, the maximum requalification test period is 10 years. 78 FR 1092 , Jan. 7, 2013, as amended at 82 FR 15891 , Mar. 30, 2017; 83 FR 55810 , Nov. 7, 2018; 85 FR 83401 , Dec. 21, 2020; 87 FR 44997 , July 26, 2022 As amended at 82 FR 15891 , 3/30/2017; 83 FR 55810 , 12/7/2018; 85 FR 83401 , 1/20/2021; 87 FR 44997 , 8/25/2022