Are you normally not in an air-conditioned environment (like at home)? If so the your body is probably just not used to it and extreme changes in temperature can cause a sickly feeling. Also, how cold do they keep it? If it's very cold compared to the weather outside, that might be the reason. And how often do they replace the filters at your work? Maybe they need to be replaces now, but then again if it happens in your car too, then that's probably not the cause. Anyway, if you're really concerned, you may want to ask your doctor or at least phone the office and ask if it's anything you should be concerned about enough to come in. Take care and I hope you get this figured out soon! :)