Regulation 18 External openingsI1

All external openings which lead to compartments assumed intact for the purposes of calculating the subdivision index “A”, and which are below the final waterlines, shall be watertight.

External openings required to be watertight in accordance with paragraph (1) shall be of sufficient strength and, except in the case of cargo hatch covers, shall be fitted with indicators on the bridge.

Openings in the shell plating below the deck limiting the vertical extent of damage shall be kept permanently closed while at sea. Any of these openings which may be accessible during the voyage, shall be fitted with a device which prevents unauthorised opening.

Notwithstanding the requirements of paragraph (3), the Certifying Authority may authorise the opening of specific doors, at the discretion of the master, if it is satisfied that such opening is necessary for the operation of the ship and provided that the safety of the ship would not be thereby impaired.

Every watertight closing appliance which is required to be permanently closed at sea to ensure the integrity of an external opening shall be provided with a notice affixed to it stating that it is to be kept closed at sea; provided that manholes secured by closely bolted covers need not be so marked.