First Alert SC-9120B Hardwired Smoke and Carbon Monoxide Alarm with Battery Backup 2 Pack

Price: $102.99
(as of Sep 16, 2026 12:12:15 UTC – Details)


The First Alert BRK SC-9120B Hardwired Combination Smoke and Carbon Monoxide Alarm uses electrochemical CO sensing technology and Ionization sensor for smoke detection. This hardwired dual CO smoke alarm can be connected to other compatible BRK or First Alert hardwired CO smoke detectors within a single-family residence.
Hardwired CO smoke alarm features battery backup for constant monitoring
Can connect to other compatible BRK or First Alert CO smoke detectors
Lights indicate if the alarm is for smoke or for carbon monoxide
Single test silence button for simple operation
Side-load battery compartment for convenience
Customers find the smoke and carbon monoxide alarm to be an exact match for First Alert SC9120B units, fitting perfectly in the old 9120B bracket and requiring no changes to existing wiring. Moreover, they appreciate its functionality and value, with one customer noting it works seamlessly with their existing system. However, the battery life receives mixed reviews, with some praising its performance while others report issues, and several customers mention their alarms started chirping.