46 CFR §154.902

1. (a)Vessels certificated to carry flammable cargo in cargo containment systems with full secondary barriers must have an inert gas system or onboard storage of inert gas that provides enough inert gas to meet the requirements of § 154.1848 for 30 days consumption.
2. (b)Vessels certificated to carry flammable cargo in cargo containment systems with partial secondary barriers must:
   1. (1)Have an inert gas system or onboard inert gas storage that can inert the largest hold and interbarrier space so that the oxygen concentration is 8 percent or less by volume; and
   2. (2)Meet paragraph (a) or (c)(2) of this section.
3. (c)Vessels certificated to carry only nonflammable cargo in cargo containment systems with secondary barriers must:
   1. (1)Meet paragraph (a) of this section; or
   2. (2)Have air drying systems that reduce the dew point of air admitted to hold or interbarrier spaces below the temperature of any surface in those spaces or −45 °C (−49 °F), whichever is warmer.
4. (d)Vessels with refrigerated independent tanks type C must have inert gas or air drying systems that reduce the dew point of any inert gas or air admitted to the hold spaces below the temperature of any surface in those spaces or −45 °C (−49 °F), whichever is warmer.