Plenum cable insulation is typically made of what material, making it more expensive?

• A. PVC insulation
• B. Teflon insulation
• C. Rubber insulation
• D. Silicone insulation

Answer: (B)

In plenum spaces, cables must minimize smoke and toxic fumes because air-handling ducts can quickly spread fire and smoke through a building. The insulation used in this setting is PTFE, commonly known as Teflon. PTFE has excellent fire resistance and very low smoke production, plus it keeps its electrical performance at higher temperatures. That combination is what makes plenum-rated cables safer, but also more expensive to manufacture, which is why plenum cable insulation costs more.

Other options like PVC, rubber, or silicone don’t meet the same low-smoke, low-toxicity requirements for plenums, so they’re cheaper but not suitable for CMP-rated cables.