Plenum cables are distinguished by jacket materials and must use what kind of plastics?

• A. Cloth jackets.
• B. Metal jackets.
• C. Flame retardant, low-smoke materials such as PVC, FEP, or polyolefin.
• D. Wooden jackets.

Answer: (C)

In a plenum space, cables must use jacket materials that are flame retardant and low in smoke because air ducts and return paths can rapidly spread fire and toxic smoke. The jacket material needs to minimize smoke and choking gases to keep occupants safer and to meet building and electrical code requirements. Materials like FEP (a fluoropolymer), polyolefin, and flame-retardant PVC are widely used for this reason—they can be formulated to resist ignition and produce much less smoke when they do burn. That’s why plenum cables are specified with flame-retardant, low-smoke plastics.

Cloth jackets would burn and generate a lot of smoke, metal jackets aren’t practical for flexible cable routing and don’t align with typical plenum-rated designs, and wooden jackets aren’t used in electrical cabling.