Safe-T-Alert 45-Series Combo Carbon Monoxide Propane Alarm Surface Mount - Black [45-741-BL]45 Series Combo Carbon Monoxide Propane Alarm Surface Mount Black Have a safe TRIP! 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: Double duty alarm Detects both gas