Info about the air quality sensor: Mill Sense Air - Mill. It measures Humidity, TVOC, Temperature and eCO2. It would be very nice to have these measurements in HA.
The sensor connects to the same Mill app that the Mill WiFi heaters use. There is already an integration for Mill heaters Mill - Home Assistant
@Danielhiversen Do you know if there are plans on adding suport for Mill sensor?
I do not have any Sense Air sensors, so would require someone else to do it.
I have the sensor but have limited time and knowledge. If you have some tips or examples for how to do this I can se what I can do or maybe some one else could help out.
Since there is no official API from Mill, you will need to decompile the Mill app or listen to network traffic from the app. It is quite a time consuming job
I have also been looking at getting that sensor and integrate with it. I was looking to check if it had API docs so I could easily make an integration and fell over this. https://api.millheat.com/ and MILL | OPENAPI APIDOCUMENT
Is this API for something else or to interact with their cloud in some way? Just wondering if you had more knowledge about that with your experience Daniel? As I might reconsider using this sensor if I have to reverse engineer the API and protocol completely.
I think you have to reverse engineer the app API. That is how it is done today for heaters
Ah okay. I’ll consider that then.
You can get a 3 pack of these sensors for 20% off from her now Mill Sense Air luftkvalitetsmĂĄler | Clas Ohlson if you like to test them out.
Ordered 
No promise for when I have time to look at it.
First version with support for Mill Sense Air: https://github.com/home-assistant/core/pull/57776
Will need to test it for a few days.
Amazing! I saw it was merged a week ago. Being unfamiliar with the update cycle for Home Assistant Core. How would I add the integration to my current home assistant core?
Do I need to manually compile and add your release in some way?
Being merged into Home Assistant, can I just update home assistant in some way and get it, or do I have to wait for next release?
And just as sanity check, will this be a new integration, or an “addition” to the Mills heating integration? (Saw a version number increase for heating on the PR).
Sorry for the questions, I just received my Mills quality sensor and wanted to get it going 
It will be part of the Mill integration in Home Assistant 2021.12
Thanks Daniel!
A few follow-up question. Does the intergration work by getting information from the cloud, or from local network? As it seems like the current intergration asks for cloud credentials. I am wondering if I have to make sure it can connect through firewall to the cloud or it’s just local traffic.
Do you have experience with connecting the mill sensor to a network with hidden ssid? Keeps failing for me, but works with a non-hidden network.
It is using the cloud, same API as the app
(I am working on an integration with local access for the Generation 3 heaters)
Ah alright. Yeah local access would be amazing when using home assistant anyway. 
Exciting. Are the mill sensors able to suport local access?
Yes, but only Generation 3 heaters
Thanks. I have tested the 2021.12 beta and its working great for my gen3 heater. But how do I know if I am controlling it local or from cloud? I See there is 2 services i can use to set temperature (Mill: Set room temperature and climate.set_temperature)
A little warning here: The Mill Sense Air are VERY unstable, even with the Mill app. I have had 5 or 6 sensors around the house and two heaters. The heaters can cope with connection for a while, but they are not care free in the long run. I have been in contact with Mill until they got fed up with my nagging, and nothing good came out of it. Mill is, as a whole, not mature enough for a stable automated home. You WILL be seeing hours and days without any reading. I ended up having a separate 2.4 ghz network for them alone, which is just plain silly.
Sorry for the long post. Here a constructive ending:
If anyone with a brighter mind than mine could find a way to integrate them without the cloud, there is a better chance for it in the open source community. I’m not sure if they use ESP32, like the heaters and even if they do, I have no clue how to hack a solution.
Are there any plans to develop local access for the Mill Sense Air indoor sensor? I’ve received a few of them today and seems only to be able to connect to them via the cloud.