What cable to use in "plenum" areas

What cable to use in "plenum" areas
Plenum cables
According to the definition from the National Electrical Code 1999 (NEC), "plenum" is "a compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system".

BICSI defines "plenum" as "a designated closed or open area used for transport of environmental air".

According to the NEC and it is the *LAW*, in plenums you *must* use plenum cables that are listed as "Type CMP"(Communications Plenum Cable). Article 800-53 of the NEC states: " Cables installed in ducts, plenums, and other spaces used for environmental air shall be Type CMP". Permitted substitution for "Type CMP" cables is "Type MPP" cables (Multipurpose Plenum Cable).

The NEC requires that "Type CMP plenum cable shall be listed as being suitable for use in ducts, plenums and other spaces used for environmental air and shall also be listed as having adequate fire-resistant and low smoke-producing characteristics".

Raceways in plenum spaces
According to the NEC Article 800-53 (a), "listed plenum communications raceways shall be permitted to be installed in plenums".

Non-plenum cables in plenum spaces
According to the NEC Article 800-53(a) "Exception", you may install Type CMR, CMG, CM, and CMX communications wires and cables in plenum spaces if they are enclosed in raceway of a type included in the NEC Chapter 3. Typically, these raceways are metal conduits.

Cable Trays in Plenum spaces
NEC Article 800-52 (d) states: "Types MPP and CMP communications cables shall be permitted to be installed in cable trays".

Check with your authorities
It is always advisable to check all your questions and NEC interpretations with your local authority having jurisdiction (local building inspector).

1. In plenums, you may install plenum cables (Types CMP, MPP).
2. In plenums, you may install general-purpose cables (Types CMG, CM, MPG, MP) and riser cables (Types CMR, MPR) enclosed in fire-proof conduits.
3. Cable trays may be used in plenums for holding plenum cables.
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