Please note that while there may be what appear to be (and may have been) covered smoking areas near exterior doors, as of 1/1/08 smoking within 15 feet of the door of a public building (and many private ones) is against the law in IL. Doors are supposed to have signs reminding people of this.
I have yet to meet anyone personally who's gotten a citation for this, but news reports indicate that it does happen from time to time. Don't give a bored cop a reason to harass you, which is always a good policy.
M