Kidde has been making residential safety alarms for decades. The 900-CUDR is a straightforward combination unit that detects both smoke and carbon monoxide from a single device. Battery power means you can install it anywhere without hardwiring, and it keeps working during power outages.

The photoelectric smoke sensor is better at detecting slow, smoldering fires than fast-flaming ones. That’s a tradeoff worth noting if you have a kitchen prone to burnt toast or a bathroom with steamy showers. The self-testing feature runs continuously in the background, so you don’t have to remember monthly button-presses. The LED indicators are clear enough at a glance, and the 85-decibel alarm cuts through ambient noise.

Two AA batteries are included, which is convenient, but you’ll want to budget for replacements about once a year. There’s no Wi-Fi or app connectivity here. This is a no-frills, reliable detector that does the basics well without adding complexity to your daily routine.