Which type of cable must be used when cabling in areas where there are forced air returns?

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The key idea is that cable in spaces where air is circulated must meet strict fire and smoke safety requirements. In a forced air return area, the cable can become part of the air path, so it needs to minimize how much smoke and toxic fumes it releases if a fire occurs. Plenum-rated cables are designed for these spaces; they use materials that produce very low smoke and limited toxic gases, helping to keep air ducts and returns safer and less contaminated during a fire.

Other options don’t address this specific safety need. PVC jackets are common for general use but can emit more smoke and harmful gases in a fire, making them unsuitable for plenum spaces. Riser-rated cables are intended for vertical runs between floors, not specifically for air-handling plenums. Shielded cables focus on protecting against electromagnetic interference and don’t tackle the fire-smoke requirements of air-return pathways.