It's a relatively new office (completely renovated fall 2006), with a new HVAC equipment/etc. I just find that I feel drowsy, less alert, with perhaps a slight reduction in my ability to concentrate, when the HVAC is blowing (it cycles on and off; maybe on for 5-10 min and then off for 30, etc..). I'm sure it's not a filter problems, since there's no perceptible odors and everything is brand new. Also, the sensation varies; usually I'm not as bothered when the ventilation/AC is functioning early in the morning (ie. 10 AM); the circulating air feels more "refreshing" then, as opposed to the afternoon when it feels more "stale" (but this could be somewhat psychological). Any ideas on what I could do to fix the problem? Any natural/organic air fresheners that could help? I don't want to use an ionizer ; I once read that air conditioners deplete the air of negative ions, but this seems like a foolish/baseless theory.