nest protect wired smoke and carbon monoxide alarm nest labs phone alerts include: low-battery smoke & carbon monoxide sensor failure split-spectrum sensor voice alarms with custom location nest app app silence detects carbon monoxide 10-year product lifetime safety checkup heads-up alerts sound check self test nightly promise pathlight steam check wireless interconnect safety history what to do home report emergency clip record with nest cam nest protect wired: three long-life backup batteries (energizer ultimate lithium “l91” aa)