The alarm started beeping on the evening of 9/3/18 . It was installed along with another First Alert alarm of the same model on 7/17/17. No other alarm is going off in the house, and I can not see anything that would cause it to go off. For my own sanity I will have to deactivate it. Why did the company say it was a TEN year alarm when it fact it lasted a little over a year? I am told my entry is too short, so I will keep typing. But to be honest, I pretty much told you everything that happened in the above. Why must I type 100 words, if I can tell you what happened in less than 100 words. Doesn't make much sense to me. I am not sure where I purchased the two alarms at. Could have been Costco, Lowe's, or Home Depot. It is hard to type 100 words when you are a wordy person, and I am not a wordy person. I like getting to the point, instead of beating around the bush. There 12 words per line and 12 lines, that should take ncare of the 100 word requirement.