I would like to share a project that I haven’t seen mentioned on the forum/official documentation. The github user bit3725 has created a custom component for connecting the Xiaomi PM2.5 sensor to HA.
I have successfully setup the component and have integrated it in my custom automation’s. The component works flawlessly for me. I also really like that the configuration is relatively simple and doesn’t require any messing around with serial connections like DIY alternatives require.
The sensor itself is pricey but I haven’t seen anything that does the job as well. It allows for you to immediately see the air quality in the room, is portable and doesn’t require a Xiaomi gateway. The only thing that is annoying is extracting the key from the Mi Home app.
Once again I didn’t create the component and all credit goes to the original author bit3725.