We've been wiring our new church building using metal boxes and MC cable. The fire alarm fellows have been running their stuff using blue plastic device boxes. Is this allowed in places of assembly? I know the 518-4 ex. It seems odd that the use of plastic would be OK under certain curcumstances but not others. But then again, that is why I'm not on a code making panel. Go fugure. Just thinging out loud.
The restrictions I see in Article 518 are for wiring methods, cables and raceways. 518.4(C)(1)does allow PVC in 15 minute fire rated walls (1/2 inch sheetrock). I am not sure how this would affect plastic boxes, this would probably be up to the building dept or the AHJ.
