Smoke Detection and Alarm Systems

What You Need to Know

Smoke detectors save lives by finding fires early. AS 1670.1 (the Australian Standard for fire detection systems) sets the rules for design and installation. The NCC (National Construction Code) Part E1 tells you which buildings need them. Get the layout wrong, and your system will not pass commissioning.

• Each point-type smoke detector covers approximately 100 m² on a flat ceiling up to 4 m high, based on spacing tables (AS 1670.1)
• Point-type smoke detectors are not effective above approximately 12 m ceiling height. Use beam detectors or aspirating systems instead (AS 1670.1)
• Place a manual call point within 4 m of every exit door from a fire compartment (AS 1670.1)
• The fire indicator panel (FIP, now formally called FDCIE) must sit at the main entrance, accessible to the fire brigade (AS 1670.1)
• Each floor is a separate detection zone. No single zone should typically exceed 2,000 m² (AS 1670.1)
• The building occupant warning system (BOWS) must reach at least 75 dB(A) for emergency tones in sleeping areas and be audible above background noise (minimum 65 dB, 10 dB above ambient) in all occupied areas (AS 1670.4)
• Systems in specific building classes must connect to a fire brigade monitoring service per NCC Specification 20 — including Class 3 buildings with detection systems (certain occupancies), Class 9a (more than 20 patients), Class 9c, and systems activating smoke control (AS 1670.3)

Take a typical 500 m² office floor with a 2.7 m ceiling. At roughly 100 m² per detector, you need at least 5 point-type smoke detectors on that floor. Room shape and obstructions usually push that number higher. Each detector sits on the ceiling, spaced so no point is more than approximately 5.8 m from a detector. The detectors wire back to a fire indicator panel (FIP) at the ground-floor main entry.

Add a manual call point beside every exit door. On a floor with 3 exit stairs, that means at least 3 manual call points. The FIP collects all signals and triggers the building occupant warning system (BOWS), which sounds an alert tone followed by an evacuation signal. The system also sends an automatic signal to the fire brigade through a monitoring service.

Higher ceilings change the rules. In a warehouse with an 8 m ceiling, smoke takes longer to reach a ceiling-mounted detector. The coverage area per detector drops, so you need more of them. Above approximately 12 m, point-type smoke detectors stop being effective. You switch to beam detectors (which sense smoke across a beam of light spanning the space) or aspirating smoke detection (ASD), which draws air through a pipe network to a central sensing unit. ASD is common in data centres, heritage buildings, and cold stores where early warning matters most.