Leading you to an educated decision.

The plenum is a space located either above a suspended ceiling or below a raised floor. Heating and air conditioning systems typically use plenum space for air circulation, and computer and telephone network wires are often routed through it. Because they are air-handling spaces that have the potential to circulate smoke and toxic fumes during a fire, plenums require "plenum-rated" halogen-free cables that resist flame spread and produce very little smoke when burned.