Heavy-duty plenum cable ties. Most commonly used in plumbing, electrical (low and high voltage), heating or air conditioning (HVAC) applications where ductwork or plenum cable (CAT5) is being installed in dropped ceilings or below raised floors. Other applications that may require plenum include fire alarms and security safety systems, computer installations and network cabling. Constructed of a specialized nylon that is self-extinguishing and releases non-toxic fumes in the event of a fire, which makes our plenum cable ties paramount for reducing risk in air handling spaces.