Fire Sprinkler Systems
Fire Sprinkler Systems is the design and performance domain: hazard classification, water supply, hydraulic calculation, sprinkler selection and spacing, and acceptance criteria. The exam expects you to move from an occupancy description to a defensible design and to spot a calculation that cannot work.
Design approach
NFPA 13 permits density/area, special design, and limited pipe-schedule methods; most NYC commercial work uses density/area. Classify the occupancy first-light, ordinary, or extra hazard-because that sets density, remote area, and sprinkler spacing. Confirm the water supply from a flow test: static, residual, and test flow. Available pressure must cover sprinkler demand, hose allowance, elevation, and friction.
Hardware
Standard spray upright/pendent maximums are commonly 15 ft spacing/225 ft² per head in light hazard, 15 ft/130 ft² in ordinary hazard, and 12 ft/100 ft² in extra hazard. ESFR and CMSA heads have their own rules and are not interchangeable. K-factor, temperature rating, and response type must match the design.
Worked example
A light-hazard office uses a 1,500 ft² remote area at 0.10 gpm/ft². Sprinkler demand is 150 gpm. Add the 100 gpm hose allowance at the supply: 250 gpm. If the area is dry-pipe, increase the remote area by 30% before calculating; the hose allowance is still applied at the supply, not at the sprinkler.
Traps
Using a 0.10 density for ordinary hazard; omitting hose allowance; treating static pressure as available; ignoring ceiling slope and obstructions; mixing K-factors without recalculating; forgetting the dry-pipe area increase.