[slavik81]

What's the dust that coats everything stored in a parking garage? Is that tire dust or something else?

[Two4]

Tire and brake dust, sand, little bit of grease, some soot settling out of the smog, maybe some salt (if you're by the sea)

[hinkley]

Or in an area that salts the roads in winter.

[voidfunc]

I used to have an apartment abutting a parking garage and also above a busy three lane road.. the worst black dust and grime everywhere. Pretty sure moving out of that apartment probably added years back to my life.