(a) The fire detection system must be divided into separate zones to restrict the area covered by any particular alarm signal.(b) All spaces in a fire detection zone must be accessible from one to another without leaving the deck involved. All doors in watertight subdivision bulkheads and main vertical zone bulkheads must be assumed closed for the purpose of this requirement.(c) The fire detection zone must not include spaces on more than one deck, except:(1) Adjacent and communicating spaces on different decks in the ends of the vessel, having a combined deck area of not more than 3,000 feet.(2) Isolated rooms or lockers in such spaces as mast houses, wheelhouse top, etc., which are easily communicable with the area of the fire-detection circuit to which they are connected.(d) The fire detection zone must not include more than 50 protected rooms or spaces.(e) Individual tubing circuits must not contain more than 1,000 feet of pneumatic tubing or its equivalent. However, more than one tubing circuit may be included in the same fire detection zone.CGFR 65-50, 30 FR 16940, Dec. 30, 1965, as amended by USCG-2012-0196, 81 FR 48258 , July 22, 2016