Why are there false alarms from my smoke alarm?

Question

Why does my smoke alarm go off when I can’t see any smoke? Are these false alarms?

Answer

Any of these situations can cause unwanted alarms:

Your smoke alarm may need to be relocated.

Ideally install smoke alarms at least six meters from appliances like stoves and ovens, which produce smoke particles. Alarms should be at least three meters from high humidity areas like showers and laundries, and at least one meter from heating or air-conditioning vents.

Your smoke alarm may need to be cleaned.

Alarms may look clean, but dust can accumulate inside the cover, even in newly-built homes. Gently vacuum your smoke alarm regularly using a soft brush attachment. If possible, take them down and give them a shake to dislodge internal dust – a can of compressed air may assist but do not spray them up-close and right inside the alarms.

An insect infestation may set off your alarm.

Clean the smoke alarm with the soft brush attachment on your vacuum. To prevent repeat problems, clean and treat the surrounding area with insect repellent. DO NOT SPRAY THE SMOKE ALARM DIRECTLY WITH LIQUID REPELLENTS OR CLEANERS.

Smoke in the air from local fires or hazard reduction burns.

Smoke alarms are sensitive, and can activate even with a seemingly small amount of smoke in the air. Local fires and hazard-reduction burn-offs can cause enough smoke to set your detectors off, especially if they have not been cleaned and maintained – the combination of dust and smoke in the air may together be enough to reach the point where they calculate that an alarm is necessary. Take the opportunity to clean your smoke detectors by following our advice, especially vacuuming and dislodging any potential internal dust.

Alarm was triggered from another part of the home.

In a system of interconnected AC or AC/DC alarms, the unit triggering the alarm may be in another part of the home – smoke may be present, but you can’t see it.

Power interruptions to 240v smoke alarms.

These smoke alarms may alarm briefly when power is interrupted, then restored. Power interruptions are common in areas where Power Companies switch grids in the early hours of the morning.

A loose electrical connection on 240v smoke alarms.

With 240v smoke alarms, loose connections can intermittently disconnect power to the smoke alarm. The effect is the same as a power failure. When power is restored, the units may alarm briefly.

Reset your alarms.

Finally, you can try resetting your alarms by pressing the test/hush button for at least 20 seconds, even whilst it is sounding.