Am I correct that pvc conduit is allowed for essentially all low-volt conductors in a theater (according to 520.5(A) exception and handbook commentary)? Also, would pvc be among the code-compliant wiring methods for circuit and feeder conductors below a wood floor of an old theater? A wood floor obviously is not "fire rated construction". Purhaps the existing wood floor would not meet current building code?

Theatres are SO touchy that you can't make your plans based upon the NEC.

You always need to touch base with the Fire Marshal.

The last theatre I worked on -- quite a while back -- the FM restricted PVC usage to below slab. The transition to EMT had to occur dang near flush with the slab.

PVC decays into cyanide gas and soot during partial combustion. Consequently many FM will not tolerate PVC since this result can be triggered by fires not started by the Low Voltage conductors.

Don't be surprised if plenum rated cables become necessary.

In my personal opinion, pvc should not be allowed no matter what. However, the NEC , the NEC handbook, and a third-party handbook I have, all state that the rule does not directly apply to the communication, A/V, and fire alarm wiring. For these systems we are instructed to use their respected code articles. Those individual code articles simply say to use chapters 1-4 (specifically 3 of course). Obviously, different cities/municipalities can make up whatever rules they see fit. At present, I am only interested in national code. Thank you for your response Tesla.

I agree with Tesla. In any "assembly" the fire code official is the king of the hill. You can meet the NEC and still not make them happy.

Agree with Tesla & Greg on the Fire Official.

Between the Building Codes and NFPA Fire Codes, any exposed PVC is not allowed. Products of combustion; flammability, flame spread, etc.

No conduit is exposed, pvc or otherwise.