46 CFR § 153.486 - Design and equipment for removing NLS residue by ventilation: Categories A, B, C, and D.
(1) Openings in the tank deck near the sump or suction point;
(2) If the openings required by paragraph (a)(1) of this section are insufficient, an access opening for visually determining whether liquid remains in the sump area of the cargo tank after ventilation or some other means for making this determination; and
(b) Unless the ship operator shows that the ventilation equipment specified in this paragraph will be available from shore when needed, if NLS residue is to be removed from a cargo tank by ventilation, in addition to the equipment required under paragraph (a) of this section the ship must have -
(1) Portable forced air ventilating equipment fitting the ventilation openings required in paragraph (a) of this section and able to ventilate the extremities of the tank to the extent prescribed in Appendix C of the IMOStandards for Procedures and Arrangements for the Discharge of Noxious Liquid Substances, Resolution MEPC 18(22), 1985; and
(2) A connector that allows a fan or air supply to be connected to the hose connections for the tank at the manifold.