Safe-T-Alert Combo Carbon Monoxide Propane Alarm - Surface Mount - Mini - 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. Package Contents: Safe-T-Alert Combo Carbon Monoxide Propane Alarm Safe-T-Alert 25-742-BL: Combo Carbon Monoxide Propane Alarm - Surface Mount - Mini - Black