Noun
Definition of Plenum: The plenum refers to an enclosed space or chamber above the drop-down ceiling or under raised floors used to provide air circulation, heating, ventilation, and HVAC systems within a building.
Plenum is also used in networking to refer to cables rated for use within plenums—thus, plenum-rated cables. Plenum-rated cables are also known as Communications Multi-purpose Plenums (CMP). They have a higher flame rating and pose a lower risk of spreading fire or introducing toxic smoke within the plenum and, by extension, a building's airflow.
When installing a cell phone signal booster, use plenum-rated cables to meet the code and safety standards. The best way to ensure this is to have your signal booster professionally installed by a reputable company.
The most commonly non-plenum cables include communications multipurpose riser (CMR) and communications multipurpose cables (CM).
| Type | Fire Resistance | Applications | Jacket Material | Toxic Fumes | Cost |
|---|---|---|---|---|---|
| CMP | High fire resistance | Rated for use in plenum airspaces | Fire-retardant PVC or FEP Jacket | Produces low levels of toxic fumes | Most expensive |
| CMR | Moderate fire resistance | Used in vertical applications and risers | Standard PVC jacket | Produces higher levels of toxic fumes | Less expensive than CMP |
| CM | Minimal fire resistance | Fit for non-fire code rated applications | Standard PVC jacket | Produces higher levels of toxic fumes | Least expensive |
Example of Plenum in a sentence
"Building codes require that only plenum rated cables are used in plenum spaces."
Related Terms for Plenum