The typical life span of a First Alert carbon monoxide alarm is 5 years. After 5 years any alarm should be replaced with a new CO Alarm. Alarms may have an actual life span that is shorter due to environmental conditions and may need to be replaced sooner. Test them weekly and if a problem arises while still under warranty, please contact Consumer Affairs, 3901 Liberty Street Road Aurora, IL 60504 or 800-323-9005 7:30AM-5:00PM CST, for a replacement. Batteries should be replaced as needed for those alarms requiring them.