Which statement about cables installed in plenum spaces is true?

• A. They can be any standard building cable regardless of fire rating.
• B. They must be plenum-rated to meet fire and smoke requirements.
• C. They must be redundant with shielded coax.
• D. They are prohibited in most building spaces.

Answer: (B)

Plenum spaces are air-handling pathways, so cables run there must not fuel a fire or release large amounts of toxic smoke as air is moved through the system. Plenum-rated cables are specifically tested and rated to limit flame spread and smoke generation in these spaces, helping to keep the building safer and meet fire-code requirements. That’s why the statement is true: cables in plenum spaces must be plenum-rated to meet fire and smoke requirements. The other ideas miss the safety and code-requirement reality—ordinary cables aren’t automatically acceptable in plenums unless they have the proper rating, redundancy with shielded coax isn’t a plenum requirement, and plenums aren’t prohibited—they just require the correct plenum-rated construction.