As far as I can tell, there is no way to block outside air from entering my
'87 Vanagon. Most vehicles have recirculate/fresh control which
accomplishes this. I _think_ I understand the heater controls, but maybe
not. I just want to be able to block diesel fumes from entering the cabin
when I'm sitting behind a bus (as in Greyhound). Should I pack gas masks?

-Mark McCulley