I live in a flat in the UK. The flat is about 6 years old, and I moved in 4 years ago.

The flat has a built in smoke-detector, and over the past few days, it has started 'going off' for about 10 seconds. This is very loud beep, not just a 'chirp' - that same noise you get if you press the 'test' button. This has happened twice in the last 4 days (while I've been present, at least).

Searching online has suggested I might need to replace the battery. However, I can't see any way to remove the casing from the ceiling. I'm somewhat hesitant to start jamming a screwdriver in, or pulling anything too hard.

My questions are therefore:

  1. Does this beeping likely mean the battery needs replacing?
  2. How can I remove the casing in order to replace the battery?

(Below, three different sides of the alarm)

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  • Some smoke detectors have to be replaced when there batteries fail. Getting a photo of the name / brand would be helpful.
    – Ed Beal
    Sep 7, 2021 at 18:16
  • @EdBeal I haven't been able to find a name on the device itself, but this did inspire me to check the pack of information I was given when I moved in. I've located the following manual, although I'm not sure which of the models I have manualslib.com/manual/752847/Brk-Electronic-650m.html
    – Korosia
    Sep 7, 2021 at 18:31
  • Typically, smoke alarms like this can be removed from their base by rotating the unit. The triangles visible on the side are a clue, as when putting the alarm back, these indicate that the unit is properly attached to its base. Also, the battery can normally be accessed by pulling on the cover of the unit, which should hinge open. Sep 9, 2021 at 12:44

2 Answers 2


Usually turn them to remove/replace. The two triangle shapes in centre of first picture seem to be alignment marks.

Usually recommended to replace batteries every six months, spring forward/fall back.

It could also be a hardwired unit that does not contain a battery, and could be time to replace unit, they have a ten year life usually.


I've now found the instructions manual included with the house move, which sheds more information. This particular unit appears to be a BRK 770MBX.

Do I need to replace the battery?

The instructions seem pretty clear that the 'low battery' warning is a small chirp every 45 seconds, not a short sounding of the alarm. I've changed the battery anyway, just in case.

The instructions suggest that dust can also be a problem, and recommends vacuuming the unit (and, if you haven't cleaned the flat recently, I'd suggest vacuuming everywhere else too!)

How can I remove the casing in order to replace the battery?

Firstly, turn off the relevant fuse. The mechanism doesn't twist, but instead the two locks on either side (e.g. in picture 2) need to be pulled outwards using a flathead screwdriver. See this instructional video

When you replace the battery, the alarm will start sounding. You can turn this off using the test button on the front.

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