Add radon device class for sensors

[jrbeilke]

Context

With the addition of the Airthings integration (https://www.home-assistant.io/integrations/airthings/) there are now devices and sensors tracking Radon levels (ie. Airthings View Plus), but Home Assistant does not currently offer a device class to handle units for these measurements.

For instance the Airthings API tracks Radon in becquerels (Bq/m³), but in the US picocuries (pCi/L) are more commonly used, and the current Home Assistant integration only supports the native unit of measurement (becquerels). This is confusing for Home Assistant users in the US (and elsewhere that are using Imperial units), as there is no easy way to change the units displayed for Radon levels of their devices.

Here are some links for additional context regarding measurement of Radon levels:

• https://help.airthings.com/en/articles/3119854-radon-what-is-the-difference-between-pci-l-and-bq-m3
• http://www.hec.uconn.edu/documents/MicrosoftWord-LM_04_What_are_units_formeasuring_9-26-06.pdf

Proposal

Similar to what was done with the air quality units (ie #573), I propose adding a new radon device class for sensors to Home Assistant, with support for unit conversion of becquerels and picocuries based on the imperial vs metric unit setting.

This would not only benefit the Airthings integration today, but also other air quality/monitoring integrations that include devices/sensors for tracking Radon levels as well.

Here is my pull request for adding the new radon device class: home-assistant/core#66149

[MartinHjelmare]

Please try to list all the existing integrations in Home Assistant that could leverage this new device class and also potential new integrations known in the market that would benefit if integrated.

[jrbeilke]

Sure, a quick search in Gitlab shows that the Airthings integration is the only one that specifically has a radon SensorEntity currently in Home Assistant.

There is potential in the future for a Radon FTLab integration to support their RadonEye device, which is commonly used to measure Radon levels at home: http://radonftlab.com/radon-sensor-product/radon-detector/rd200/
(the RadonEye device measure levels in picocuries instead of becquerels like Airthings so unit conversion would be handy)
ie. https://community.home-assistant.io/t/radoneye-ble-interface/94962

This device class could also be used with sensors from the ESPHome integration in Home Assistant that are used to measure Radon, such as the Airthings Wave Plus and other devices that use Bluetooth ie.
esphome/feature-requests#147

[jrbeilke]

Found one more radon sensor in Home Assistant custom-components:
https://github.com/custom-components/sensor.airthings_wave

[jrbeilke]

Almost forgot the new EcoQube Radon detector from Ecosense/FTLab. No Home Assistant integration yet that I'm aware of, but definitely seems to have potential:
https://ecosense.io/pages/ecoqube

[ch0gan]

Is this idea dead? In addition to the need for radon unit conversion,


I also noticed pressure comes to HA as mbar but the imperial unit is hg.

[bdr99]

@ch0gan, the issue with the pressure unit for Airthings will be fixed in HA 2024.4. The fix was merged in home-assistant/core#113005.

[bdraco]

picocuries and becquerel are both units of measure of radiation. I think this makes more sense as a radiation sensor device class.

[jcgillespie]

picocuries and bequerels are both units of measure for radiation, but these devices aren't measuring strictly radiation. They measuring the radioactivity in a specific volume of air.

[jcgillespie]

I created a PR to implement this before realizing it would need a discussion in the architecture repo first.

[abmantis]

I am not sure if a device class should be this specific, since radon is just one gas out of many (despite being the one that most people will be affected by/deal with). Still, should the proposal be for something like radiation concentration instead?

[jcgillespie]

I suggested that as well in #886 . I think the challenge will be balancing a larger change that is correct against a smaller immediately valuable change that may make future expansion harder.