46 CFR § 153.314 - Ventilation of spaces not usually occupied.
(a) Each tankship must have portable ventilation equipment that fits the mount required in paragraph (b)(1) of this section.
(1) A mount for the portable mechanical ventilation equipment required by this section; and
(2) Either permanent ventilation ductwork connected to the mount and arranged to supply air to the extremities of the space; or
(3) An attachment for temporary ductwork at the mount with enough ductway in the ventilated space and temporary ductwork stowed aboard the vessel to supply air to the extremities of the space.