Which NEC section pertains to wiring in plenums and other air-handling spaces?

• A. 300.22
• B. 300.4
• C. 310.15
• D. 600.58

Answer: (A)

Wiring in ducts, plenums, and other air‑handling spaces must meet special fire and smoke safety requirements because moving air can rapidly spread flames and toxic fumes. In these spaces, conductors must be installed only in a listed raceway or be cables that are specifically listed for plenum use, and certain non-plenum cables are not allowed. This ensures that the materials won’t contribute heavily to fire growth or emit dangerous smoke when heated. In practice, you’d either run wires in conduit with individual rated conductors (like THHN/THWN) or use plenum‑rated cables (with jackets allowed in air‑handling spaces). The other options cover areas unrelated to this environment, such as general protection from damage or ampacity calculations.