Fire Alarm Detector Spacing & Coverage

Secondary (standby) power calculation — NFPA 72 §18.3.7

Dwg No.FA-001

ScaleNTS

MethodNFPA 72

Rev—

Preliminary screening aid only. This tool applies the standard NFPA 72 Chapter 17 smooth-ceiling spacing rule (nominal listed spacing, 0.7x rule for maximum point-to-detector distance, <=15 ft from a wall) using a simplified rectangular grid solver. It does not model beamed/sloped ceilings, high air-flow returns, or the Annex A adjustment figures in detail -- rooms with those conditions, or ceilings above 40 ft not using a performance-based design, must be laid out by a qualified fire alarm professional per the current NFPA 72 edition and Annex A guidance.

Detector Type & SpacingTag, detector type, listed nominal spacing

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Room / area tag Detector type

Listed nominal spacing (ft)

Room GeometryDimensions, ceiling height and type

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Room length (ft) Room width (ft)

Ceiling height (ft) Ceiling type Performance-based design in use (required if ceiling >40 ft)

Corridor Mode (optional)Single-row centerline layout for narrow corridors

Result - Detector Layout

Detectors required

Worst-case point distance

0.7x spacing limit

Grid spacing used

Max wall distance

Room area

Area per detector

Layout Diagram

schematic grid, to scale

Include Calculation Ledger in report Include OhmZone brand mark in report

Report template (.docx, optional)

Calculation Ledger

clause-by-clause