Bests & Worsts Reviews from Amazon

This air quality meter must be calibrated every time you turn it on. This makes it completely useless for anything other than a basic temperature reading. You must set the device somewhere with "fresh" air, and after the calibration, this becomes the zero point for each sensor. This means that, if your fresh air is dirty, you can't measure anything. Let's say I want to measure the particulate counts in my bedroom. I'd start the device up, leave it outside for three minutes while the calibration runs, and then bring it inside. Because of the pollen outside, the device took that as "fresh" air, and since my indoor air happens to be cleaner, the device displays a big fat zero for the PM10, PM2.5, and PM1.0 counts, making it useless for actually measuring particulate counts. I verified this by leaving it in my room for the calibration process, seeing that the PM counts were at/near 0, and then I took it outside, where the PM counts almost immediately went up. Tl;dr: This device can only make RELATIVE measurements. If your reference air is dirty, e.g. there's formaldehyde or particulate in your outdoor/fresh air, you can't gather any useful data.