The smoke detectors in my house are hard-wired. The one in the basement and one in a bedroom keep chirping about every 30 seconds. I vacuumed both of them; the one in the bedroom stopped chirping for 3 days. The basement one started chirping again after only 2 days. This has now been going on for over a week and is driving me nuts!!! I tried vacuuming them again to no avail. Please, please, please advise.