First Alert has been making residential smoke alarms for decades, and the SMI105-AC is a clear step forward in reliability. The headline feature here is the Precision Detection sensor, which is designed to reduce false alarms from cooking or steam while still catching real threats quickly. That matters more than most people think—nuisance alarms are the top reason homeowners disable their detectors entirely.

This unit hardwires into your existing AC system and can interconnect with up to 18 other compatible alarms. When one detects smoke, all of them sound. The real safety net is the sealed 10-year lithium battery backup. If the power goes out during a fire, this alarm keeps working for a full decade without any battery swaps. The battery is non-replaceable, which means the entire unit gets replaced at the ten-year mark—standard practice for modern smoke alarms.

One limitation worth noting: this is a smoke-only detector. It does not sense carbon monoxide. The white plastic housing is utilitarian but unobtrusive on a ceiling. For a hardwired setup that prioritizes long-term reliability over flashy smart features, the SMI105-AC is a solid, no-nonsense choice.