i have a job in long island new york and , would like to use 4" pvc to pull the communication wires threw , the wires are plenum rated, but a rival contractor saw the pvc in the drop cealing and and made a big mes for me, can anyone tell me if it is ok to run pvc in the drop cealing if a plenum return exists? and what artical in the 2005 code i can find it in so i can either fix this problem or make this contractor happy. please help!