The life expectancy for Carbon monoxide alarm is 5-7 years, depending upon the alarm manufacturer. http://www.mass.gov/eopss/agencies/dfs/dfs2/osfm/pubed/fs-topics/fs-topics-a/carbon-monoxide-safety.html

Beginning in March 2007, UL 2034, the standard for single and multi-station carbon monoxide (CO) alarms, required that all CO alarms have an audible “end of life” warning. The end of life warning alerts you that the unit has reached its expiration and should be replaced. Some manufacturers have voluntarily included this warning on their products since 2001; pursuant to UL 2034, any CO alarm manufactured after April 2007 with a UL listing must include an end of life warning.” www.ncdoi.com/osfm/journal/articles/2011/080411c.pdf

Laws. “A number of states have statutes that require carbon monoxide detectors in certain residential buildings. In addition, Virginia allows tenants to install carbon monoxide detectors in rental properties if they believe it is necessary to ensure their safety. Texas requires carbon monoxide detectors in certain day-care centers, group day-care homes, and family homes. Connecticut and Maryland require installation of carbon monoxide detectors in schools.” Please see the listing by state for a summary of the laws. http://www.ncsl.org/research/environment-and-natural-resources/carbon-monoxide-detectors-state-statutes.aspx

What is your system to replace the detectors? Do you replace them prior to their life expectancy expiring or only when the “end of life” warning starts beeping?