Live radiation monitoring for Home Assistant

Every click,
on your dashboard.

Follow any Geiger counter on radmon.org, or your own. Counts per minute, dose rate, an online check and a radiation alert, with history and statistics built in.

Open in HACS Owner or public? Releases

CPM + µSv/h Radiation alert Any public station Owner API mode

What you get

One device per station, with sensors that behave like Home Assistant expects: proper device classes, long-term statistics and translations.

CPM and dose rate

Counts per minute plus µSv/h, from the station itself or calculated with a conversion factor you can tune to the tube.

Radiation alert

A safety binary sensor that turns on at or above a CPM threshold you set. Hook it up to any notification.

Online check

Know when a station stops reporting, including your own counter at home.

Location built in

Coordinates, place name and counter model as attributes and on the device page.

Keeps working

A failed poll keeps the last good reading. Diagnostic sensors show poll health, and diagnostics redact your password.

Plays nice

radmon.org is run by volunteers. Radmon polls gently and identifies itself, so the service stays up for everyone.

Owner mode or public mode

Enter a password and you're in owner mode. Leave it empty for public mode. You can switch later with Reconfigure.

Owner mode

For your own station, with its data-sending password
Uses radmon.org's official lastreading API, which needs the password since May 2026
Your station's own µSv/h value
Every 5 minutes by default, down to 1 minute

Public mode

For any station, just the name
Reads the small public station page
µSv/h calculated from CPM (default factor 0.0057, SBM-20)
Every 30 minutes by default, minimum 15, to go easy on radmon.org

Entities you get

One device per station (Radmon lImbus).

sensor.…_cpm: counts per minute
sensor.…_dose_rate: µSv/h
sensor.…_last_reading: reading timestamp
binary_sensor.…_online: readings are fresh
binary_sensor.…_radiation_alert: CPM ≥ threshold

Plus diagnostic sensors (consecutive errors, last update status and time), disabled by default.

Options

Update interval: 5 min owner · 30 min public
Conversion factor: 0.0057 µSv/h per CPM
Alert threshold: 100 CPM
Offline after: 30 min

A daily watcher checks that the radmon.org endpoints still answer as documented and opens an issue if they change.

Act on it

Get a push notification when the alert turns on, or when your own counter stops uploading. Long-term statistics make a 7-day CPM graph a one-card job.

Radmon is not a safety device. Readings come from volunteers' hardware and can be late or wrong.

triggers:
  - trigger: state
    entity_id: binary_sensor.radmon_limbus_radiation_alert
    to: "on"
actions:
  - action: notify.mobile_app_your_phone
    data:
      title: "☢️ Radiation alert"
      message: "{{ states('sensor.radmon_limbus_cpm') }} CPM"

Installation

HACS, a restart, and a station name.

HACS

1. Click Open in HACS, or add https://github.com/DonTranQuiL/HA-Radmon as a custom repository (category Integration).
2. Download Radmon and restart Home Assistant.
3. Settings → Devices & services → Add integration → Radmon, then enter a station name from the station list.

Upgrading from 1.x

Existing entries migrate to public mode automatically and keep their entity IDs and history. Delete the old custom_components/ha-radmon folder after updating.

Full docs, dashboard YAML and troubleshooting are in the README.

Every click,on your dashboard.