When I first received this CO2 monitor I was impressed with the packaging. The quality of the packaging was similar to what you would expect with high end electronics. It came with the usb cable needed to plug it in but you have to use your own USB adapter, which I’m sure most people have plenty of. Once I let it charge I followed the steps to calibrate it, which was easy to do.
I have no other way to check my CO2 levels but I will say that after calibration I trust it. The temperature and humidity readings match the values listed on my homes thermostat. If I stand near the unit the CO2 raises, if I pick it up and breath into the unit the CO2 level goes really really high, when I took it outside the reading dropped, and after I’ve been away from home all day the reading is lower. All of those are exactly what you would expect it to do. It only has a few buttons for the basic functions of turning the alarm on and off, changing the temp scale from Celsius to Fahrenheit, turning the unit on/off, and turning the backlight off.
My only critiques about the unit is that just off of the battery it will only last about 24 hours with the backlight always on, so if you plan to always leave it on to measure CO2 it will need to be plugged in, or charged daily. The backlight is pretty bright, which is great in a well lit area but it’s a little to bright IMO in a dark room.
Overall if you need to know your CO2 levels (I was trying to decide if I should add a HRV to my homes HVAC) then this unit is easy to setup and the CO2 level is incredibly easy to read. It worked perfectly for my needs.