46 CFR §76.27-30

1. (a)The fire detection system must be divided into separate zones to restrict the area covered by any particular alarm signal.
2. (b)The fire detection zone must not include spaces in more than one main vertical zone, except on cabin balconies.
3. (c)The fire detection zone must not include spaces on more than one deck, except—
   1. (1)Adjacent and communicating spaces on different decks at the ends of the vessel having a combined ceiling area of not more than 3,000 sq ft;
   2. (2)Isolated rooms or lockers in such spaces as mast houses or wheelhouse tops, which are easily communicable with the area of the fire detection circuit to which they are connected; and
   3. (3)Systems with addressable detectors and manual alarm stations that can have their status individually determined.
4. (d)Any fire detection zone with non-addressable detectors and manual pull stations must not contain more than 25 protected rooms or spaces.