First Alert has been the go-to for residential safety for decades. The SC9120B-3 stands out because it combines both smoke and carbon monoxide detection in one hardwired unit, then backs it up with a sealed battery. That battery means your protection doesn’t stop when the power goes out.

The unit uses an electrochemical sensor for CO and a photoelectric sensor for smoke. Photoelectric sensors are better at catching slow, smoldering fires before they become raging ones. The alarm hits 85 decibels, which is loud enough to wake you from deep sleep. Installation is straightforward if you have existing hardwired wiring, and the 3-pack covers a typical two-story home with a basement.

One honest limitation: these are standard detection units, not smart detectors. There is no Wi-Fi or phone alert. If you want push notifications when you are away from home, you need to look at the First Alert Onelink line instead. For a straightforward, reliable safety system that works every time without an app to manage, this 3-pack is the practical choice.