QP Pro 2 Air Quality Monitor

It’s small and unobtrusive, quiet, and keeps me reassured that my house air quality is good.

Cool device great design and does what it says plus remote access with an app

Everything is great except...um, they aren't accurate.

You should buy 2 of these and run them side by side. If you are like me, you won't get the same TVOC or RH readings from your 2 units. Both units give me the same Temperature and PM 2.5, but any cheap device can measure those things. The CO2 readings are close enough. But the RH and TVOC are not. RH readings on one unit are off by 10% (as confirmed by 3 independent hygrometers), and the TVOC readings on one unit are 3 to 10 times higher than on the other (which is the difference between GOOD and DANGEROUS). Which unit is right? Maybe if I bought a 3rd one I could hazard a guess. In short, these devices are probably fine for determining whether TVOC is changing up or down over time, or whether it is higher in one room than another, but they are not well-calibrated and you can't take the actual numbers they produce seriously.