“Hazardous area” means an area in which explosive gas-air mixture are, or may be expected to be present in quantities such as to require special precaution for the construction and use of electrical apparatus or other apparatus which otherwise would constitute a source of ignition;
“Hazardous zone or space” means
(i) spaces containing flammable cargo or spaces adjacent to cargo tanks;
(ii) all enclosed and semi-enclosed space with direct access to hazardous zones or spaces;
(iii) an enclosed space situated in a hazardous zone or space may be regarded as non-hazardous provided it is separated from liquid cargo spaces by at least two gas tight steel bullheads or decks, with no direct opening into hazardous zone or space and is mechanically ventilated.