Section 154.405 - Design vapor pressure (P[o]) of a cargo tank(a) The design vapor pressure (Po) of a cargo tank must be equal to or greater than the MARVS.(b) The Po of a cargo tank must be equal to or greater than the vapor pressure of the cargo at 45 °C (113 °F) if: (1) The cargo tank has no temperature control for the cargo; and(2) The vapor pressure of the cargo results solely from ambient temperature.(c) The Po of a cargo tank may be exceeded under harbor conditions if specially approved by the Commandant (CG-ENG).CGD 74-289, 44 FR 26009, May 3, 1979, as amended by CGD 82-063b, 48 FR 4782, Feb. 3, 1983