Safe-T-Alert FX-4 Carbon Monoxide Alarm - 2-Pack [FX-4MARINE2-PACK]FX 4 Carbon Monoxide Alarm 2 Pack Marine Use Low Voltage Hard Wired Alarm. Replaces your CO alarms that are over 5 years old. No Bags. No Tags. Full 5 Year service life, longer than CO Sentinel CMD 4M alarms. CMD 4M and CMD 3M that have reached end of life. Features: Conforms To ANSI UL STD 2034 Marine Meets ABYC A 24. NMMA Listed Component Most Reliable Boats DC electrical system or marine grade batteries supply power to the alarm No missing or dead