Definition(s)
Main Vertical Zones
Main vertical zones are those sections into which the hull, superstructure and deckhouses are divided by “A” class divisions, the mean length and width of which on any deck does not in general exceed 40 m. <Chapter II-2, part A, regulation 3>.
Source: IMO Resolution MSC.99(73), amendments to the International Convention for the Safety of Life at Sea, 1974, as amended, 5 December 2000, International Maritime Organization. Legislation