Safe-T-Alert Combo Carbon Monoxide Propane Alarms Flush Mount - Black. Test and inspect the Propane and CO alarms installed in your RV every week and replace malfunctioning alarms.Replace all Propane and CO alarms that are 5 years old or older.Install alarms listed for RV use.Prevent accidents by teaching family and friends about the operation of the alarms. Never ignore a sounding alarm. Features of Safe-T-Alert Combo Carbon Monoxide Propane Alarms Flush Mount Double-Duty Alarm. Detects both gas leaks and CO gas simultaneously. Reliable 12V power means no missing or dead batteries to replace Durable and built for the extreme RV environment Meets RVIA/NFPA requirements and is listed to UL 1484 RV and UL 2034 RV Dimensions: 6-3/8" W x 3-1/2" H x 1-77/200" D. Package Contents: Safe-T-Alert Combo Carbon Monoxide Propane Alarms Flush Mount Safe-T-Alert 35-742-BL: Combo Carbon Monoxide Propane Alarms Flush Mount - Black