I wonder if it's agreable to work in an office which is filled with fog and only has a limited number of light beams through that fog.
Granted that's not the data center itself, it's in an adjacent human-friendly workspace, but even those computers can't be too wild about mist/smoke.
http://en.wikipedia.org/wiki/Indoor_air_quality
http://en.wikipedia.org/wiki/Radon#Health_Risks_and_Epidemio...