Considered this too, but there are two reason I ruled it out: 1. The beep was very long - maybe a second or two - much longer than smoke alarms. 2. I could hea

Considered this too, but there are two reason I ruled it out: 1. The beep was very long - maybe a second or two - much longer than smoke alarms. 2. I could hear it blocks away from my apartment. No smoke alarm chirp would carry that far.