What are the main types of smoke detectors used in Australian commercial buildings?

Australian commercial buildings use five smoke detector types: point-type photoelectric (most common, for standard offices and retail), optical beam detectors (for warehouses and atriums with high ceilings), aspirating smoke detection or ASD (for data centres and high-value spaces), multi-sensor detectors combining smoke and heat (for kitchens and false-alarm-prone areas), and video smoke detection (for very large open spaces, requiring a performance-based fire engineering solution). AS 1670.1 and the AS 7240 series govern their design and installation.

What is the maximum ceiling height for a point-type smoke detector in Australia?

Under AS 1670.1, point-type smoke detectors are not effective above approximately 12 metres ceiling height. Above this height, beam detectors or aspirating smoke detection (ASD) systems must be used instead.

When should you use aspirating smoke detection instead of point-type detectors?

Use aspirating smoke detection (ASD) in data centres, server rooms, clean rooms, heritage buildings, and any space where very early warning is critical. ASD draws air through a pipe network to a central sensing unit and detects smoke minutes earlier than point-type detectors. It costs 3-5 times more per zone but hides hardware in the ceiling void.

How do you prevent false alarms from smoke detectors near kitchens?

Use multi-sensor detectors that combine smoke and heat sensing. They only alarm when both thresholds are met, which cuts false alarms from steam and cooking fumes. NCC 2025 Specification 20 allows alternative detector types where spurious alarms are likely, as long as the detector is deemed suitable per AS 1670.1.

What area does a point-type smoke detector cover in Australia?

Under AS 1670.1, a point-type photoelectric smoke detector covers approximately 100 square metres on a flat ceiling up to 4 metres high. The exact spacing is calculated from the standard's spacing tables, which require no point to be more than 7 metres from the nearest detector and no more than 10 metres between detectors.

Smoke Detector Types and Selection

Section 1

What You Need to Know

Not all smoke detectors work the same way. AS 1670.1 (the Australian Standard for fire detection systems) and the AS 7240 series define five detector types, each suited to different spaces. Pick the wrong one and you get false alarms, failed commissioning, or gaps in coverage. This memo explains each type and where it belongs.

Section 2

The Rules

Point-type photoelectric detectors cover roughly 100 m² on a flat ceiling up to 4 m high. Spacing tables set the exact layout (AS 1670.1)
Point-type smoke detectors are not effective above 12 m ceiling height. Use beam detectors or aspirating systems instead (AS 1670.1)
Aspirating smoke detector (ASD) sampling point spacing must not exceed point-type detector spacing limits (AS 1670.1)
Beam detectors need an unobstructed line of sight between transmitter and receiver, spanning up to 100 m. No point in the protected area should be more than 7.5 m from the beam centreline (AS 1670.1)
In Class 9a health-care buildings, photoelectric smoke detectors must be installed in patient care areas and exit paths (NCC 2025 Specification 20)
Where detectors are likely to cause false alarms (kitchens, loading docks), any other detector type deemed suitable per AS 1670.1 may be used instead (NCC 2025 Specification 20)

Section 3

What This Means in Practice

For a standard office with a 2.7 m ceiling, point-type photoelectric detectors are the default choice. They are cheap, reliable, and proven. At roughly 100 m² per detector, a 500 m² floor needs at least 5 point-type smoke detectors. Room shapes and obstructions usually push that number higher. These detectors respond well to slow-smouldering fires that produce visible smoke.

When the ceiling goes above 4 m, smoke takes longer to reach a ceiling-mounted detector. The coverage area per detector shrinks, so you need more of them. Above 12 m, point-type detectors stop working reliably. A warehouse with a 15 m clear height needs beam detectors or aspirating smoke detection (ASD). Beam detectors span up to 100 m across the space and suit warehouses, atriums, and hangars. ASD draws air through a pipe network to a central sensing unit and gives the earliest possible warning, making it the standard choice for data centres, server rooms, and heritage buildings.

Kitchens, loading docks, and workshops create steam, fumes, or dust that trigger false alarms from standard photoelectric detectors. Multi-sensor detectors combine smoke and heat sensing in one device. They only alarm when both thresholds are met, which cuts false alarms without slowing response to real fires. The NCC allows these as an alternative where spurious alarms are likely.

Section 4

Key Design Decisions

1

Point-Type Photoelectric vs. Aspirating Smoke Detection

Use point-type photoelectric detectors for offices, retail, and corridors with ceilings up to 12 m. Switch to ASD for data centres, server rooms, clean rooms, or any space where minutes of extra warning time matter.

Trade-off: ASD costs 3-5 times more per zone than point-type detectors. It detects smoke earlier and hides all hardware in the ceiling void, but the pipe network needs regular maintenance to stay clear.

2

Beam Detectors for Large Open Spaces

Use beam detectors in warehouses, atriums, and hangars where ceilings exceed 6 m and floor areas are large. A single beam detector pair can cover a 100 m span, replacing dozens of point-type detectors.

Trade-off: Beam detectors cost more per unit but need far fewer devices for large open areas. They require a clear sightline, so coordinate with bulkheads and future partitions early.

3

Multi-Sensor Detectors for False-Alarm-Prone Areas

Use multi-sensor (smoke + heat) detectors near kitchens, loading docks, and workshops. The NCC allows alternative detector types where spurious alarms are likely.

Trade-off: Multi-sensor detectors cost more than standard photoelectric detectors, but they cut false alarm callouts and tenant complaints.

4

Detector Type Drives the Whole System Design

Confirm the detector type for each zone before starting system design. ASD needs pipe routing in the ceiling void. Beam detectors need clear sightlines. The choice affects cable runs, FIP zone configuration, and commissioning procedures.

Trade-off: Changing detector types after design locks in cable routes causes rework. Decide early in schematic design, not during construction.

Section 5

Who Needs to Know What

Section 6

References

AS 1670.1:2024, Fire detection, warning, control and intercom systems — System design, installation and commissioning — Fire
AS 7240.7, Fire detection and alarm systems — Point-type smoke detectors using scattered light, transmitted light or ionisation
AS 7240.12, Fire detection and alarm systems — Line type smoke detectors using a transmitted optical beam
AS 7240.15, Fire detection and alarm systems — Point-type fire detectors using smoke and heat sensors
AS 7240.20, Fire detection and alarm systems — Aspirating smoke detectors
National Construction Code 2022, Volume One, Specification 20
AS 3786:2023, Smoke alarms using scattered light, transmitted light or ionisation

Smoke Detector Types and Where to Use Each

What You Need to Know

The Rules

What This Means in Practice

Key Design Decisions

Point-Type Photoelectric vs. Aspirating Smoke Detection

Beam Detectors for Large Open Spaces

Multi-Sensor Detectors for False-Alarm-Prone Areas

Detector Type Drives the Whole System Design

Who Needs to Know What

Need this engineered for your project?

References

Related design memos

Smoke Detection and Alarm Systems

Emergency Warning and Intercommunication Systems (EWIS)

Stairwell Pressurisation Systems