Hope to have planted a helpful seed... There are times you can get in there with it but have another switch inside so you can turn on and off the airflow of the booth fan before opening the door..
The exhaust fan doesn't have to be on all the time. But you do need filtered air going in while the bad air is going out. Once the fog is gone turn it off. It is even off during clearing and then turned on after the last of the clear is sprayed to prevent that cloud of over spray from landing on the part(s)