Fire Protection, Detection, and Suppression Systems
Sprinklers: hazard first, then numbers
Automatic sprinkler review starts with occupancy hazard classification, because hazard sets density, design area, and hose allowance. Light hazard usually designs near 0.10 gpm over 1,500 sq ft; ordinary hazard groups step up from there; extra hazard is higher still. Design may be hydraulic (density/area method, with a full calculation) or, in narrow cases, pipe schedule. The reviewer checks coverage and spacing limits, water supply duration and flow test data, sprinkler temperature rating and clearance, and whether the waterflow alarm, FDC, and control valves are correctly arranged. Standpipes follow NFPA 14; fire pumps follow NFPA 20; inspection, testing, and maintenance follows NFPA 25.
Detection and notification
NFPA 72 governs. Spot-type smoke detectors on a smooth ceiling are spaced at 30 ft, which yields about 900 sq ft per detector and roughly half-spacing to walls. Pull stations go near the exit at roughly 42 to 48 in. above the floor. Notification appliances must be audible above ambient and visible with candela selected for the room size and, in sleeping areas, for the required response.
Traps
- Selecting a density that matches a similar-sounding occupancy rather than the classified hazard.
- Accepting a calculation with no water supply curve or with the hose allowance omitted.
- Approving detector layout drawn at 30 ft but placed with more than the permitted distance to the wall.
- Confusing design standards (NFPA 13) with maintenance standards (NFPA 25).
Rule of thumb
If a number appears without a hazard classification and a cited table, it is not a reviewable design. Worked example: on a smooth, flat ceiling, detectors at 30 ft on center stay within 15 ft of the wall - measured diagonally, not just in plan along one axis.