What is Plenum?
We are often asked by installers, both small and large, what does “plenum” mean? Even by those that have been doing installation for years, so don’t be ashamed if you’re not sure either. Today, we will clear that up and also explain to you whether you really do need plenum cable or not for your installation project.
First of all the word plenum refers to a space, usually above a ceiling or below a floor, that can serve as a receiving chamber for air that has been heated or cooled to be distributed to inhabited areas. In simplified terms: it is the space above a building’s dropped ceiling or below a raised floor that gets used for heating, ventilation or air conditioning often known as HVAC.
What Does Plenum Have to Do with Cabling?
In addition to HVAC usage, plenum spaces are often used to house networking cables being run throughout a building. The cables used to run through these plenum spaces are referred to as Plenum Cable or abbreviated as CMP. The difference between plenum cable and other cables are the jacketing material. True plenum cable uses flame retardant low smoke materials such as Teflon FEP, should there be a fire the cable would emit minimal amounts of harmful fumes compared to lower grade jackets.
Why Do I Need Plenum Cable?
It all boils down to safety. Plenum cable goes through extensive flame tests to adhere to UL and National fire Protection Association standards. Plenum cable is less hazardous and emits the lowest amount of fumes should there be a fire. Legally, it is required by National electrical Code NEC if you’re installing any cabling in plenum areas. It’s necessary since plenum cables are installed through air circulation spaces which has very few fire barriers, they require coating that will not add to the spreading of flames.