As we walk through this world we pick up contaminates. If you are dealing with circuit boards you need to have cleanliness standards in place to mitigate these problems.
Human beings hands are covered in contaminates like sodium, chlorine, and many other salts, all of which are damaging to PCB's.
If you are dealing with power supply boards that have large traces, then you can probably get away with minimum cleanliness standards.
On the other hand if you are sellingfine line laminate substrates, almost no level of contamination will be acceptable.
As a minimum people should not handle PCB's with bare hands.
I do not think you have to single out smokers as a particular source of contamination. You just need to have good cleanliness working standards.
