Section 2(2) in The Merchant Shipping (Crew Accommodation) Rules, 1960
(2)Unless the context otherwise requires, no structure shall be deemed to be watertight, gastight, or oil tight for the purposes of these rules unless all openings in that structure, other than ventilation opening necessary for the admission of air from passageways to sanitary accommodation, laundries, drying rooms or galleys, are provided with means of closure which will enable such openings to be made watertight, gastight or oil tight, as the case ma be.
