Barely used Origins Air Quality Monitor (originall 500RMB). Works great to give you confidence that the air purifiers are working. http://originstech.com/products/laser-egg/ Contract through WeChat ID...
BramC BR-Air-330 air quality monitor is a real-time air quality monitoring instrument used to detect PM2.5 and formaldehyde concentration in the indoor environment. It’s a great tool to control...