300.22(C) covers environmental air spaces, see the FPN, and prohibits cord wiring.
(C) Other Space Used for Environmental Air.
This section applies to space used for environmental air-handling purposes other than ducts and plenums as specified in 300.22(A) and (B).
It does not include habitable rooms or areas of buildings, the prime purpose of which is not air handling.
FPN:The space over a hung ceiling used for environmental air-handling purposes is an example of the type of other space to which this section applies
(1) Wiring Methods. The wiring methods for such other space shall be limited to totally enclosed, nonventilated, insulated busway having no provisions for plug-in connections, Type MI cable, Type MC cable without an overall nonmetallic covering, Type AC cable, or other factory-assembled multiconductor control or power cable that is specifically listed for the use, or listed prefabricated cable assemblies of metallic manufactured wiring systems without nonmetallic sheath. Other types of cables and conductors shall be installed in electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, rigid metal conduit without an overall nonmetallic covering, flexible metal conduit, or, where accessible, surface metal raceway or metal wireway with metal covers or solid bottom metal cable tray with solid metal covers.
CORDS ARE NOT PERMITTED IN THIS SPACE
