Adding EU Radiation Monitoring to Home Assistant

I've been slowly building out my environmental monitoring setup at home, tracking all the usual suspects: temperature, humidity, air quality, and so on. However, there was this nagging gap in my data collection that I didn't even realize existed until I stumbled across the European Commission's radiation monitoring network (REMAP JRC). I thought, "Huh, I wonder if I could get this into Home Assistant?"

Why bother with radiation data?

Let's be honest: tracking background radiation isn't a pressing need for most people. It's not like I'm living next to a nuclear plant (though if you are, this might be pretty useful). But I've come to appreciate comprehensive environmental data; radiation is just one more piece of that puzzle.

It's also fascinating to see how background radiation fluctuates naturally. For example, did you know heavy rainfall can increase local radiation readings for a short while by bringing down radon from the upper atmosphere? I also didn't until I started monitoring it!

The API struggle

The REMAP JRC API is quirky. The data comes back with strange encoding issues with station codes like "EE20395" returning as "êèëáí" in the response. Weird.

How it works

The integration is pretty straightforward. It connects to the REMAP JRC network once an hour by default, fetches the data for your local monitoring station, and converts the raw values to actual radiation readings in nanoSieverts per hour (nSv/h).

The conversion uses this formula:

actual_value = raw_value / (1001 - stamp)

Where stamp is a random number between 20 and 999 that's generated when you set up the integration. Why this formula? Don't ask me; it's just how the API works. I suspect it's some normalization factor that varies by station.

Setting it up

Getting this running is pretty simple:

1. Install the integration via HACS or manually add it to your custom_components folder - Github
2. Find your local station code from the REMAP JRC map
3. Add the integration through the UI and enter your station code
4. Give it a name that makes sense to you
5. Done!

The integration will appear as a sensor with a radioactive icon and display readings in nSv/h. You'll also get additional attributes like the raw value, timestamp, and station details, which you can use in templates if you're into that sort of thing.

Some practical stuff you can do with it

I've set up a simple automation that notifies me if radiation levels jump significantly:

automation:
  - alias: "Radiation Level Alert"
    trigger:
      platform: numeric_state
      entity_id: sensor.radiation_tallinn
      above: 150
    action:
      - service: notify.mobile_app
        data:
          title: "Unusual Radiation Level"
          message: "Current level: {{ states('sensor.radiation_tallinn') }} nSv/h"

This will probably never trigger except after heavy rain, but it's there just in case.

I've also added the radiation sensor to my "Environment" view alongside temperature, humidity, and air quality. It gives me a complete picture of what's happening around my home.

What I've learned

This little project is part of a broader effort to reclaim more control over my data. While radiation monitoring isn't sensitive personal information, having this data in my system is still satisfying.

The whole integration is open source, so you can check the code, suggest improvements, or adapt it for your needs. I don't claim it's perfect, but it does what it needs to do with minimal fuss.

If you're already tracking environmental data in Home Assistant, adding radiation monitoring is a small but interesting addition. It's not changing your life, but it's one more piece of the environmental puzzle you can own rather than relying on external services or apps.

Get it running

The integration can be found on my GitHub repo or through HACS. If you try it out, I'd love to hear how it's working for you or what you're using it for.

I should probably add a disclaimer: While this integration pulls data from official monitoring stations, it's primarily meant for educational and informational purposes. If there's an actual radiation event, please listen to emergency services rather than relying solely on your Home Assistant dashboard.