Cabling
Plenum-Rated Cable
Also called: CMP, plenum cable
Cable with a fire-resistant, low-smoke jacket required by code in air-handling plenum spaces — typically the void above a suspended ceiling used for return air.
The requirement exists because a plenum shares air with the occupied space: a burning PVC jacket there distributes toxic smoke building-wide. Plenum-rated CMP is mandatory in those spaces; riser-rated CMR is for vertical shafts between floors, and general-purpose CM for neither.
Using the wrong rating is a failed inspection and a re-pull, not a warning — and it is the fastest way to blow a schedule on an occupied building. Jacket rating is verified against the mechanical drawings before ordering, because 'above the ceiling' does not always mean plenum, and assuming either way is a coin flip.
Related terms
- Structured Cabling
- A standards-based cabling system built as an organised hierarchy — entrance facility, backbone, telecom rooms, horizontal runs, work area outlets — rather than point-to-point runs added as needed.
- Firestopping
- Sealing cable penetrations through rated walls and floors with tested assemblies so the barrier's fire rating is restored.
- Ceiling Tile Speaker
- A loudspeaker installed into a suspended ceiling grid, used in distributed arrays so coverage is even across a room instead of loud at the front and thin at the back.
More Cabling terms
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