內循環is very bad for health, should only be used occassionally

When to use inner circulating? Only when hitting dust storm, or strong odd smell or smoke outside, or quickly to lower inner temperature. Inner circulation should only be in a flare, not for regular driving.

Foggy on windows can be cured by pointing air outlets to windows, not only front windshield, but also side windows. Check your manual or ask people who are familiar with your model/year car...