https://www.googlenestcommunity.com/t5/user/viewprofilepage/user-id/48946 . I just saw your message. The National Fire alarm code requires that all smoke alarms sound throughout a home. If you only replace one of the smoke alarms in your home the others will not sound together when the Nest Protect sounds an alarm and visa versa. You would normally replace all of your smoke alarms in your home with new smoke alarms of the same make and model
