Dead Air Space
Nuisance alarms can be a pain, but the real problem is the smoke alarm that doesn’t go off because it’s in the wrong spot. Putting alarms in ‘dead air space’ means that smoke doesn’t reach them until it’s too late and they simply can’t do their job of alerting you to a fire. Dead air space refers to areas that trap hot air, preventing smoke reaching the alarm.
It’s why you always see alarms positioned away from the corner where the ceiling meets the wall. That’s a dead air space and so is the apex of cathedral ceilings. Essentially you shouldn’t hide smoke alarms in corners – they have to be out and proud. Exposed beams create corners as well. The rule is to place alarms at least 300mm from corners.