Bergen, Norway, is an example of a city surrounded by mountains where the air quality can get very bad, terrible for asthmatics. This phenomenon is called inversion. Before the symptoms begin, the asthmatic person may alleviate the symptoms by measures such as traveling to locations with inversion during summer and observing bad geographic landscapes so avoiding them altogether such as strong winds blowing directly to valleys with clouds very low, hardly seeing sun. Instead of asking directly list-style question "What are cities in the world that asthmatics should avoid due to poor air quality?":
What are the measures an asthmatic traveller can make to choose new travelling locations not affected by inversion?