Hello I have a question about plenum ceiling. In my company we use our drop ceiling for a return air for a/c. So it is considered a plenum ceiling. All the cable for low voltage or high voltage has to be a plenum rated. Right now I had to install on the ceiling Christmas lights. To power them up I had to use some extension cords over the ceiling. The question is: Is it okay to use them temporary in the Plenum ceiling? They are probably will be there less then a month and will be deinstalled. I can't find anything in the code about temporary wires in the plenum ceiling. Thanks.:-?