Pull the air through a cold condenser, to condense out anything volatile in it. It is is a fog when you pass through, it will be ready with a little cooling to condense. Then do a GC analysis on the condensate.
But you'd have to take it straight to the GC because somebody at the airport would likely see you up to something, have a closer look, and you would not get a package unobserved/unintercepted to the lab.
A used GC is probably about $5 grand.