You might not need to completely enclose your machine. The chemical and electronics industries use exhaust hoods in their "nasty fumes" departments. They partition 3 sides of the work station and the hood sits on top. The air flow captures 100% of the noxious stuff.
Then there is the question of how to filter the captured air. You probably can't just vent to the outside (osha, epa, other regs?).
I don't have a link handy but Altavista or google will no doubt turn up hours of reading material.
robotic regards,
Tom