Abstract: A battery operable dangerous condition warning device adapted to issue an alarm when a sensed dangerous condition exceeds a predetermined status incorporates a monitoring device circuit including: a processor, a dangerous condition sensor, a horn, a battery condition monitoring procedure cooperating with the processor to periodically check the integrity of the battery for detecting a first battery integrity condition in which battery failure can be expected after a relatively long period and a second battery integrity condition in which battery failure is imminent. The circuit further implements an audio low battery warning generator adapted to drive the horn to issue a distinctive audio warning (e.g.