Final answer:
Non-plenum rated cables can be used in a plenum space if they are enclosed in fire-resistant conduit or raceway, as the area is air-circulative and a potential fire hazard that is regulated by the NEC.
Step-by-step explanation:
Cables that are not plenum rated can only be used in a plenum space if they are enclosed in conduit or raceway that has the proper fire-resistance rating. A plenum space is a part of a building that can facilitate air circulation for heating, ventilation, and air-conditioning systems, typically in the space between a drop ceiling and the structural ceiling, or under a raised floor. The National Electrical Code (NEC) sets out strict regulations for cabling in these areas because of the potential fire hazards. Non-plenum cables release toxic fumes when burned and are a greater fire spread risk, which is why plenum-rated cables, which are coated with fire materials, are normally required.