Years ago when Teachers Smoked in Class and I had a Company repairing Apple II, Research Machines and BBC micros the damage from Cigarette Tar was staggering...
I don't know about "biohazard", but it can certainly be nasty. It's no wonder either that it's a PLUS point in Car and Electronic Gear sales when they say from a "non-smoker" home.
I have always wondered can the tar vapour or smaller volatile particles get in to the HDD surface via the breathing hole filter? HDDs are absolutely not hermetically sealed.
Some discussions here: http://discussions.virtualdr.com/archive/index.php/t-178020.html
(Safety Goggles and mask...)