The foam inside the ducts has deteriorated and fallen onto the outlet registers at the carpet level.
Foam released from some areas inside the ducts
Dime size chunks completely covered some outlets
Bosrescope in duct
Possibly the situation was made worse because earlier in the year, the airplane had lost a APU seal and put oil residue in the entire condition system. this may have caused the foam to finally release.
There is foam sheet mufflers on each register, drilled t match the holes in the register. Also deteriorated, but that did not seem to be the worsen problem.
the small pieces of loose foam was blown toward the registers, and completely covered a few of them.
We used a vacuum and a bore scope to clean out the ducts.
the rest of my notes are here