I am wiring an office that has a suspended ceiling that serves as a return air space above it. Code book says I can use ent above suspended ceilings if it is fire rated at 15 minutes. It doesn't say I can't use it either in this situation. In the Nec it does say that ent is flame retardent. Can I use it? What is your opinion.

No.

-Hal

300-21(c)1.no ENT

Thanks guys, I missed that in the code book.