No, your Wave Radon is always on and always measuring your radon levels.
The data collected by Wave Radon is saved logged locally on the device, and becomes visible in the Airthings App/ Dashboard as soon as you sync your device again. Wave Radon stores all measurements locally on the device itself for 80 days.
Once you sync to the App, it allows you to visualize your radon levels on your phone or tablet, and see how radon, temperature and humidity has behaved over the past 48 hours, 1 week, 1 month, and 1 year.
The Airthings app supports background sync, so your Wave Radon can sync automatically without you needing to open the app manually. For best results, make sure you are running the latest version of the app, have Bluetooth enabled, and that your phone is not in battery optimization mode. You can also open the app manually and pull to refresh to trigger an immediate sync. Once synced, all measurements saved on the monitor will upload to the cloud and be available in the app or from your online dashboard at https://dashboard.airthings.com/