What type of jacket is on plenum cables?

• A. Standard rubber jacket.
• B. Aluminum outer jacket.
• C. Nonfire retardant plastic jacket.
• D. Fire retardant plastic jacket of either low smoke PVC or FEP.

Answer: (D)

When cables run in air-handling spaces (plenums), the jacket must minimize fire growth and smoke to keep the area safe and maintain airflow during a fire. That means the jacket needs to be fire-retardant and produce low smoke. Among the options, only a fire-retardant plastic jacket that is specifically low-smoke—either low-smoke PVC or FEP—meets this requirement and is considered plenum-rated. Standard rubber jackets, non-fire-retardant plastics, or metal jackets do not provide the necessary plenum fire and smoke performance, so they aren’t appropriate for plenums.