The meat packing places I have done PVC is required. You also have to use clamps that hold the conduit off the wall. I use 2 hole PVC straps that suround the pipe, they hold the conduit 1/8" off the wall so the pipe does not trap crud aganst the wall. Rod http://www.plumbingsupply.com/pipeclamps.html edit to add link
[This message has been edited by livetoride (edited 08-26-2006).]