U UNNI’s CO2 monitor uses a photoacoustic sensor. That’s a more stable and accurate technology than the cheaper NDIR sensors found in many budget monitors. It means you can trust the number on the screen to actually reflect your indoor air quality.

The display shows real-time CO2, temperature, and humidity. You can set custom alerts for when CO2 climbs past a healthy threshold, with three volume levels to choose from. It runs on USB power with a battery backup, so it won’t blink off during a power outage. The backlight adjusts to three brightness levels, making it easy to read day or night.

You’ll need to supply your own batteries. The design is simple and functional, a white rectangle meant to sit on a shelf or desk without fuss. For checking ventilation in a home office or ensuring a bedroom stays fresh overnight, it provides reliable, quiet oversight.