From the consumer side:

I've bought a Qingping ClearGrass Air Monitor (CGS1). It costs about $100, but has CO2, tVoc, PM 2.5, PM 1.0, temperature and humidity sensors. From what I've read, sensors are quite good, people only sometimes complaining for bad fans, that need to be fixed after a year or so of use. Everything in one nice USB-C powered case with a sensor screen. A bit too much animation once a minute, that can't be disabled. Data is sent by WiFi.

There is a Qingping App for Android and IOS with some graphs and insight into values, but not much. It also can be integrated with Mi Home, but doesn't work for my region, and I can't get token to talk to it with python-miio, as in this habr example [1]. This example doesn't work too [2], looks like the api has changed.

So after a bit of sniffing I've made a simpler solution:

1. Installed Mosquitto MQTT Broker on my home gateway

2. Made a DNAT redirect of qing.cleargrass.com requests to this broker:

  iptables -t nat -A PREROUTING -i br-lan -p tcp -d qing.cleargrass.com --dport 11883 -j DNAT --to-destination 127.0.0.1:11883

3. Added a cron job of periodic subscribing for air monitor data. Without this message it doesn't push the data. The topic consists of some base64 uid and air monitor MAC address, I wrote it in square brackets, should be changed by end user:

  */5 * * * * /usr/bin/mosquitto_pub -h 127.0.0.1 -p 11883 -t '/[uid]/[mac]/user/get' -m '{"duration":"303","up_itvl":"2","type":"12"}'

4. Configured a mqtt_consumer in telegraf:

  [[inputs.mqtt_consumer]]
    servers = ["tcp://127.0.0.1:11883"]
    name_override = "air_monitor"
    topics = [
      "/+/+/user/update",
    ]
    data_format = "json"
    tag_keys = [
      "mac",
    ]

5. Created graphs and alerts in grafana. It was easier for me to create a further automation from there.

It is sad that there are still no easy way to connect everything in a "smart" home.

[1] https://habr.com/en/post/482352/#comment_21085236 [2] https://habr.com/ru/post/493220/

Edit: formatting