First Alert has been making residential safety gear for decades, and the BRK SC9120LBL solves a specific annoyance: dead backup batteries. This hardwired smoke and CO alarm ships with a sealed 10-year lithium battery that you never have to swap. The drawer is pre-locked so you cannot remove it prematurely. That means no chirping at 2 AM and no annual chore of replacing 9V cells in every unit.

The unit combines an ionization sensor for fast-flaming fires with an electrochemical sensor for carbon monoxide. It runs on standard 120V AC wiring but the lithium backup keeps it running during power outages. At 10 years, the entire alarm gets replaced, not just the battery. That is the trade-off. You lose the flexibility of swapping batteries, but you gain a decade of zero maintenance.

The alarm is loud at 85 decibels and includes a test/silence button for nuisance triggers. It lacks smart home connectivity, so no phone alerts or voice integration. If you want app control, look elsewhere. For a straightforward, code-compliant unit that stops demanding your attention, this is a solid choice.