Storing a scope in a garage

I've seen lots of photos of folks storing their scopes in garages whether they're Dobs or SCTs on wheelie-bar-type contraptions. Assuming the scope is not stored in an air-tight container (I've never seen a big Dob close-up...do the mirror boxes close up air-tight when not in use?), does anybody know the risks of storing a scope in a garage that's used? Specifically, I'm curious about the effects of typical "garage fumes" (engine exhaust, gasoline vapors from the lawn mower, etc) on optics that are not stored in an air-tight container. Am I being too paranoid when I insist on storing my LX200 in the house?