... CO alarm SCM03:Battery operated Carbon Monoxide Alarm can prevent you fromHarm of gas leakage. It uses the most ... , water heater.So to be safty,we suggest you to install CO alarm in kitchen,wash room,dinning ... low voltage warning and testing.If it alarm when you press the testing button for several seconds, the ... unit work normally.It use less power,you only need to change battery once a year.Working ...