Last night we experienced what is probably the Smoke Alarm equivalent of Chinese Water Torture – a seemingly unstoppable, almost random intermittent beeping from one of our mains powered Smoke Alarms.
Like all new houses in the UK over the past few years, our house was built with mains powered smoke detectors, one of which is placed in the hall downstairs, and the other in a similar position on the upstairs landing. Being mains powered we’ve not really thought much about them – they are basically just there, and get periodically tested – usually thanks to something cooking.
Anyway, last night, the detector downstairs started beeping. It wasn’t regular, but was fairly frequent – frequent enough to be annoying. I took a look, and written on the case was that it had a battery backup, to ensure the alarm worked even if the mains supply failed, so perhaps it was the battery. We turned off the mains circuit for the smoke detectors, and after a bit of fiddling managed to remove the unit, only to find that the battery was a 9 Volt PP3 and typically we didn’t have any of those sitting around. More than that, with the battery disconnected, the smoke alarm then beeped again a couple of times – obviously some backup of the backup… Ok, new batteries it was, so off I went to one of the local convenience stores, and while I was at it, I got a second battery so we could change the one in the unit upstairs too.
I came back with the new batteries, and we replaced them in both units, and what happened – within a few minutes it started beeping again.
I went and took down the unit, and then looked up on the Internet for any clues as to the problem. The main suggestion I could find was that something was that there was a build-up of dirt and fluff on the sensor – indeed I remembered something similar causing a fire evacuation when I was working at SSE. So out came the vacuum cleaner, and I ran it all around the vents on the unit, and replaced it on the ceiling. About five minutes later it did give a couple more beeps – but since then, nothing, so hopefully it is now all sorted. The unit in question is right outside the kitchen door, so is exposed to a lot more dirt and fluff, so that does explain it – the lesson being, periodically vacuum your smoke alarms!