No wiring of any type shall be installed in ducts used to transport ______.
b) flammable vapors
c) loose stock
d) all of the above
See answer and applicable Code reference
The correct answer is: d) all of the above
Article 300 covers the general requirements for wiring methods for all wiring methods, unless modified by other Articles in the Code. Section 300.22 focuses on wiring in ducts not used for air handling, fabricated ducts for environmental air, and other spaces for environmental air (plenums). As noted in the first sentence of Sec. 300.22(A), "No wiring systems of any type shall be installed in ducts used to transport dust, loose stock, or flammable vapors."