Smoke alarms and testing

Updated 30 May 2026

Interlinked means all of them sound

In an interlinked system, one alarm detecting smoke triggers every alarm in the property. That matters at three in the morning, when a fire starting in the kitchen needs to wake somebody asleep two floors up.

Interlinking can be wired or wireless. Wireless is far less disruptive to retrofit; wired is the natural choice during a rewire when the cable is going in anyway.

Where alarms belong

• Circulation spaces: a smoke alarm on every storey, in the hallway and landing where escape routes run.
• Kitchens: a heat alarm rather than a smoke alarm, so toast does not train everyone to ignore it.
• Living rooms: a smoke alarm where the room is the principal habitable room, particularly in rented homes.
• Anywhere with a fuel burning appliance: a carbon monoxide alarm as well. Different hazard, different detector.

Testing, and the ten year rule

Press the test button on each alarm once a week. It tests the sounder and the electronics, and it takes ten seconds.

Alarms have a service life, normally ten years from manufacture, printed on the back. The sensor degrades whether or not the unit has ever been triggered. If the date has passed, replace the unit rather than the battery.

What a rewire changes

When a property is rewired, alarm provision is normally brought up to current standards as part of the work, because the cable routes are open and the cost of doing it then is a fraction of doing it later. We include it in the written scope rather than leaving it as an afterthought.