The insulation most commonly used for non plenum cables is____.

• A. PVC
• B. Teflon
• C. Polyethylene
• D. Polypropylene

Answer: (A)

The main idea here is that everyday indoor cables can use a standard, cost‑effective insulation material because they are kept in spaces that don’t require special smoke- or toxin‑releasing properties. PVC is the most common insulation for non-plenum cables because it is inexpensive, readily available, and meets typical fire-retardant requirements for general indoor use. In contrast, materials like Teflon (PTFE) are more expensive and are used in specialized applications or plenum-rated cables where very low smoke is required. Polyethylene and polypropylene exist in some cable constructions, but they are not the standard choice for the typical non-plenum building cables.