46 CFR §76.33-5

1. (a)The smoke detection system must be divided into separate zones to restrict the area covered by any particular alarm signal.
2. (b)The smoke detection zone must not include spaces on more than one deck, except the small adjacent spaces mentioned in paragraph (c) of this section.
3. (c)Each separate space must be considered as a zone, except that two or three small adjacent spaces having a combined volume not exceeding 5,000 cubic feet may be connected on the same zone.
4. (d)Where a space is of such size that one accumulator is not sufficient, not more than two accumulators may be combined in one zone.