Originally Posted by
MacGyver
Arturo... I imagine a standard air filter followed by a HEPA filter wrapped in a custom aluminum enclosure should be adequate....
If you are only doing metals a particulate filter may be adequate. If you do plastics you may find it necessary to use activated charcoal to remove the organic vapors; these are not particles and may not be stopped even by a HEPA filter.
As lamicron says fumes from melted and vaporized plastic range from nasty to very nasty; rusty machines are one thing, rusty lungs are more difficult to replace.
An open mind is a virtue...so long as all the common sense has not leaked out.