46 C.F.R. § 154.405

(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).