Why does my smoke detector alarm sound when the power goes off and comes back on?

Some smoke alarms are pow­ered by AC (alter­nat­ing cur­rent) and use a bat­tery back­up. When these units lose pow­er momen­tar­i­ly they may chirp sev­er­al times to inform you they are on back­up pow­er or are return­ing to main pow­er. For more infor­ma­tion, review the man­u­fac­tur­er’s doc­u­men­ta­tion on your type of alarm.