Kidde is recalling certain Kidde NightHawk combination smoke/carbon monoxide (CO) alarms.  The alarm can fail to continue to chirp when it reaches its seven-year end of life if the batteries are replaced, leading consumers to believe it is still working. This poses a risk of consumers not being alerted to a fire or CO incident in their home.  Kidde recommends replacing the affected units. 

See more here: 

https://www.cpsc.gov/Recalls/2017/Kidde-Recalls-Combination-Smoke-CO-Alarms