[neves]

I'm always lost when it comes to air quality meters. There are so many specifications, and in general, they're quite expensive—especially for people in third-world countries. Does anyone know a good air quality monitor that costs less than 100 dollars? Preferably one that can be purchased on a Chinese website like AliExpress.

[xvilka]

Devices below 100 usually have bad sensors so they do some black magic and a lot of approximation in the firmware/software. Good air quality meter with good sensors simply cannot cost this low, even in the economy of scale.

[Rebelgecko]

If you're willing to DIY a bit you can put together an Airgradient for under $100. Especially if you're making multiple