I have a smoke alarm (Kiddie) that is beeping regularly (every 30 seconds or so), what I would typically associate with a low battery. The strange thing is that the beeping is only happening between 5 and 8 in the morning, and I'd like to understand why.

It starts beeping when there's nobody downstairs, and it's in a back room with no close heat sources - the boiler and water cylinder are in a different room. The only thing I can think of that has changed is that this time of year the sun streams through my utility room and into the back room where this smoke alarm is located. It's on the ceiling so it gets no direct sunlight of course, but the light shines on the floor directly below it.

I've replaced the battery, so I'm not looking for advice on how to fix it, I'm curious as to what the mechanism is that's causing it.

  • Hard to say really. Could be temperature, but you probably don't have the house a whole lot below typical room temperature.
    – Nelson
    Commented Mar 30, 2021 at 9:00
  • Wondering if it is seeing dust in the sunlight beam. If it is still doing it, cover window for one morning and see if it still happens. At least it is not saying you are a bad cook.
    – crip659
    Commented Mar 30, 2021 at 11:33
  • That's a good idea @crip659, I've replaced the battery, if it keeps beeping I'll try that.
    – GdD
    Commented Mar 30, 2021 at 11:35
  • Does this answer your question? CO detector starts beeping every morning at 6am
    – isherwood
    Commented Mar 30, 2021 at 16:16
  • I can see why you think it's a duplicate @isherwood, but CO detectors and smoke detectors work on different principles so the answers aren't applicable.
    – GdD
    Commented Mar 30, 2021 at 16:24

4 Answers 4


I have noticed this same phenomenon before, and the only explanation I can think of is that early morning hours are typically the coldest hours of the day in a house.

Smoke alarms operate with a battery (sometimes only battery, sometimes the battery acts as a backup for a hardwired power source). The battery voltage is monitored, and when the voltage drops below a threshold (indicating the battery is nearly dead), the alarm starts the low battery chirp to make you put a new battery in. Battery voltage is affected by temperature, so when the temperature drops a bit, and the battery is right at the threshold between OK and low, this temperature drop might cause the voltage to drop enough to trigger the chirp. Once the battery warms up a bit, the chirp might stop.

After a few days or weeks of this, you will probably eventually get a constant chirp, and then the chirp will stop because the battery is dead (at least if the battery is the only power source).


Check the date code on the back to see how old it is. All these units have a "length of service" which is about 8 years. after that date they will beep so show that they have come to their end of life and need to be replaced. There should also be a phone number that you can call for information.


Try process of elimination. Move that smoke alarm to a different parts of the house. Or buy new one (they can be cheap or go with what you like) and see if that changes situation.


Reading online it also suggests that holding down the test button for 15 secs resets the alarm. Worth a try.

  • That doesn't do anything on this model.
    – GdD
    Commented Mar 31, 2021 at 6:57

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