FIRST ALERT Hardwired Wireless Smoke Alarm with Photoelectric Sensor and Battery Backup, SA521CN-3ST , White

Price: $76.72
(as of Oct 08, 2026 12:48:30 UTC – Details)


For those who want a comprehensive detection system without hiring an electrician or worrying about hardwiring, the First Alert SA521CN Wireless Interconnected Hardwired Photoelectric Smoke Alarm is an ideal solution. Use this smoke detector to replace an existing hardwired smoke alarm and then install additional compatible First Alert Wireless alarms for an interconnected safety network (additional alarms sold separately). Wireless technology makes it possible for the detector to connect with up to 18 compatible First Alert wireless-enabled alarms to create a wireless safety network. These connected alarms can communicate with each other and sound in unison. The photoelectric smoke sensor is designed to reduce false alarms from cooking smoke or shower steam while remaining sensitive to real danger. The smoke detector has an integrated battery backup in case of power outages and features a single button to silence false alarms and test the unit.Eco-friendly, completely recyclable as an electronic device.
The front cover design of the alarm may vary but product function remains the same
Help keep your family safe with this hardwired smoke alarm that wirelessly interconnects with other First Alert–enabled alarms to create a home safety network
Equipped with photoelectric smoke sensor optimized to detect larger smoke particles produced by smoldering fires; helps minimize the number of false alarms
Wirelessly connect up to 18 First Alert enabled alarms for the maximum in whole-home protection
Hardwired alarm includes 2 AA backup batteries for continued monitoring in the event of a power outage
Includes test/silence button, low-battery warning, EZ access battery door
First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert Brand Trust Survey in February 2018)
Customers find the smoke alarm easy to set up and install, with good wireless connectivity and loud, clear voice alerts. However, the reliability and value for money receive mixed feedback – while some say it works as advertised and is worth the money, others report units malfunctioning after two months and consider it overpriced. Moreover, customers disagree on the voice notifications, with some loving the room prompts while others find the voice feature worthless. Additionally, battery life and false alarms are concerns, with reports of units having low batteries and near-constant false alarms.