False positives

About a month ago I woke up in the middle of the night. I did not realize at first why I was awake, but all of a sudden adrenaline kicked in and I recognized the sound of my smoke detector. All four of them, that is, thanks to them being connected by radio. I checked every room in my house, only to come to the conclusion that there was no smoke, no fire, and no danger. And the smoke detectors had stopped their alarm. There was no obvious reason for them to have gone on alert.

Lessons learned: a) The wireless connection of the smoke detectors works not only in test mode, but also at 01:30 hrs. during the night. b) Children continue to sleep while a 90 dB alarm sounds in their room.

Some days ago the smoke detectors started an alarm again, this time right after breakfast. Again, all four of them made noise, and there was no smoke, no fire, no danger. This time I had to disconnect batteries to get the alarm to stop. When I re-connected the batteries, the alarm did not start again. I remembered a conversation at my previous job about reliability of smoke detectors. Even good smoke detectorsmight give you false positives (and I had selected mine based on recommendations from engineers and based on vendor-independent device test results). One of my colleagues had told me that his standard operating procedure in case of a false positive was to unmount the detector, put it in a plastic bag, seal it, and examine the bag the next morning. Often times, he would find a small insect inside the bag that had caused the smoke detector to sound an alarm.

I am not yet willing to adopt a standard operating procedure for false positives. On the positive side, I will count the one night’s false alarm as a fire exercise.

About Author: Hanno Langweg

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