Illinois does not allow AAV,s mechanical vents or any other device you can think of. They can and will fail. Here is two parts in the Illinois code that will show you they are not allowed at all in the state of Illinois. Colored Bold is added by me.
Originally Posted by ak199
Section 890.1480 Types of Fixture Trap Vents
a) Trap Vent. No trap vent shall be installed within two pipe diameters of the trap weir. (See Appendix K: Illustration N.)
b) Common Vent. A common vent, installed vertically, may be used for two fixture traps when both traps connect with a vertical waste at the same level. (See Appendix K: Illustration O.)
c) Vertical Wet Vent. A vertical wet vent may be used for two fixtures set on the same floor level, but connecting at different levels in the stack, provided the vertical drain is one (1) pipe diameter larger than the upper fixture drain and that both drains conform to Appendix A: Table I. (See Appendix K: Illustrations P and Q.)
d) Mechanical Vents. Mechanical devices shall not be installed in lieu of vent piping.
Section 890.1420 Stack Vents, Vent Stacks, Main Vents
a) Design. A properly designed and installed venting system, in conjunction with the soil or waste system, is essential to protect trap seals and prevent siphonage, aspiration, or back pressure. The venting system shall be designed and installed to permit the admission or emission of air so that under normal and intended use the seal of any fixture trap shall never be subjected to a pneumatic pressure differential of more than a one (1) inch water column. If a trap seal is subject to loss by evaporation, means shall be provided to prevent loss of the trap seal. (See Section 890.410(f).)
b) Installation. A stack vent, vent stack or a main vent shall be installed with a soil or waste stack whenever back vents, relief vents, or other branch vents are required. (See Appendix K: Illustration A.)
c) Terminal. Vents shall terminate independently above the roof to the outside atmosphere, or shall be connected to another vent at least six (6) inches above the flood-level rim of the highest fixture. (See Appendix K: Illustration B.)
d) Main Stack. Each building in which plumbing is installed shall have at least one main vent stack no smaller than three (3) inches for each building drain installed. (See Appendix A: Table K, and Appendix K: Illustration C.)
e) Building Sub-drain Sump Vent Sizes. Building sub-drain sump vents shall be sized in accordance with Appendix A: Table K.
Go to Studer's web site they will tell you which state allows their AAV's Lots of them have special circumstances that need to be met before you use one. I have seen many of these AAV's installed illegally (just because the hardware store sells it does not make it legal) and I seen many of the cause problems with trap seals being broken due to positive pressure in the system, also seen a few that got stuck in the shut position so it never admitted air like it was designed to do, and people thought they had a clogged drain till I removed the AAV.
These mechanical vents are a handy mans solution to things. If you want to protect the health of your family and your community do it right or call a plumber to do it right.