What can trigger a motion false alarm?

[JDRoberts]

This FAQ should help.

FAQ: False positives on motion sensors

Hi there, I have started to get false positives with one of my SmartThings motion sensors.Anyone any idea what that could cause this? I observed it many times with definitelty no motion at all. It was during the day. The temperature is 99F. There is a security glass door which I thought was the culprit. However when I stand there myself seeing my own reflection it does not trigger a motion alert. I have several sensors all exposed to the same kind of temperature. Is is possible that this sensor went defective? Thanks, Olaf