I have a First Alert Smoke/CO detector in the RV. My particular model isn't made any more (SCO1N). Ours runs off of a 9V battery and we change the battery once a year. Make sure you read installation instructions on how high up and where to locate your alarms. I would suggest you get one with the photoelectric smoke sensor, which reduces alarms from cooking smoke or shower steam. Mine has gone off more than once from cooking smoke (gas grill is outside the screen door and smoke blows in and a couple of times the stove top has set it off).