The e-mail question above arrived at the end of last week, I waited to post the question and my answer until I had received a response answering my question.
I received that response today and it is included below.
Answer: Illinois considers an AAV to be a "mechanical vent", one of the few places which do so.
Mr.. Jerry Peck/Codeman, You are correct sir there is not a definition in the current (2004) Illinois Plumbing Code book describing "mechanical vents".
However a Air Admittance Valve (AAV) is indeed a mechanical device whether relying on a spring or gravity to permit the venting operation to function there is movement within the device, it is not static. This movement is mechanical, therefore Section 890.1480 d) applies. Thanks, Frank.
Frank Shimkus
Plumbing Consultant
IDPH Environmental Health
Plumbing Program
I would like to thank Mr. Frank Shimkus of the Illinois Plumbing Program for responding and providing the definitive answer the question.
We now have a definitive answer from the Illinois Plumbing Department -
AAVs are considered "mechanical vents" in Illinois, which means you should NOT be finding any AAVs in Illinois.
If you inspect in Illinois and find AAVs installed, you should be writing them up for improper venting and in needed of correction.
I disagree with their position, as do most other plumbing codes, but they are the Authority Having Jurisdiction so what they say goes for their jurisdiction.
Codeman