Whenever you do anything structurally or to any mechanical system of your home, always check with your Building Inspection Department for local codes and any permit and inspection requirements.
It may not seem important to you when you do it, but if you ever sell your home, any code violation (especially any kind of safety hazard) will have to be corrected if discovered during home inspections.
Some places don't allow AAVs.
A home being sold actually only has to meet code for the year it was built, but buyers can insist on certain safety hazards changes (AAVs don't fall into that category of course).
(20+year NC real estate broker)