Currently historical measurement data is not available for different rooms from within the Airthings App. However, you can find the historical measurement information from your personalized dashboard at https://dashboard.airthings.com/. Just simply use the same log-in credentials that you use for the Airthings App. Here you can see all of current and past measurement segments.
You can also read more about the online web dashboard here on the Airthings wesbite: https://www.airthings.com/dashboard