Wiring with return air chase

Here is some wiring that in a 1970’s home that was installed in the return air chase. Since the return is considered a combustion area is there a particular kind of sleeve that the wiring can be wrapped in to protect it?



section 300.22 B of the National Electrical Code 2005 states that only wiring of type MI or MC shall be permitted in ducts or plenums specifically designed for enviornmental air

Improperly constructed plenum. Close it up and you don’t have to bother about the wires.

*[FONT=Times New Roman][size=2]Exception: This section shall not apply to the joist or stud
spaces of dwelling units where the wiring passes through
such spaces perpendicular to the long dimension of such


 300.22(B) would not be what is pictured. At best 300.21(C) is the reference here and while Picture #1 would tend to be in accordance with the exception I posted. I am not sure picture #2 is....BUT with that said it would be close enough to compliance that I would not have a problem with it. If indeed we are talking about a dwelling unit and a return air space.