For laser particle counter, i can recommend these 2 gadgets.
The RMB 429 version has formaldehyde sensor inside. The RMB 629 has a CO2 sensors inside.
https://item.taobao.com/item.htm?sp...0g7s5&id=526471566162&ns=1&abbucket=11#detail
https://item.taobao.com/item.htm?sp...0g7s5&id=526471566162&ns=1&abbucket=11#detail
Another gadget
This one can toggle between different screens and have different display readouts. But if i am not wrong, there is no option for having 1 single device to give you a smoke PM2.5, PM xx concentration (ug/m3), formaldehyde HCHO and CO2. CO2 is usually the limiting factor.
However, for some geeks, this version does give you the number of particulates count (see below), of course do not expect this to be lab-grade accurate at all, but for home/haze/air purifier and even if you use hospital grade big-ass DIY HEPA air purifier/filters that's modified from clean room equipment it's going to be more than sufficient. (can import these China machines via sea ship, actually still significantly cheaper than your Cado 310 1.1k cost

But they look somewhat industrial though some versions are pretty ok)
https://item.taobao.com/item.htm?sp...0g7s5&id=529311240188&ns=1&abbucket=11#detail