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When installing cabling in walls and ceilings it is important to use cables that meet the local code requirements. Local codes are typically based on the National Electric Code (NEC) published by the National Fire Protection Association. The NEC contains a large amount of information and covers a wide variety of electrical installations. The majority of the NEC document is devoted to electrical power installations, but it also covers the installation of other cabling that is integrated into a building's structure in any way. 

The requirements in the NEC are designed to prevent hazards to human health and safety from wiring including electrical shock, the tendency to start or perpetuate a fire, and the production of toxic fumes when exposed to fire. The NEC provides classification standards for cables with jackets that are suitable for reducing these risks, i.e. CL2, or Class 2. Almost all of these cable ratings permit in–wall installation per the NEC. In–wall cabling is typically sufficient for residential installations. The NEC also covers specialized cabling that is designed to be installed within a plenum or a riser in a structure. 

A plenum, under Article 100 of the NEC, is a compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system. Plenum spaces are primarily seen in commercial environments. An example of the most common types of plenum spaces would be a dropped ceiling or raised floor. Most homes do not have significant plenum spaces, so plenum cabling is rarely a concern for residential installations. To receive a plenum rating the cabling is required to use material in the construction of the jacket and dielectric which do not easily give off toxic fumes if burned. The reason for this is that if there is a fire in one part of the building then toxic fumes could be fed to the remainder of the building through the ventilation system. The term riser applies to a space that is not specifically defined in the NEC, but is a requirement for cabling that will penetrate from one floor of a building to another. 

Common Jacket Ratings

Rating Usage
CMPAll in-wall, plenum and riser applications. 
CMR, CL3R, CL2RAll in-wall and riser applications; not permitted in plenums.
CM, CMG, CL2In-wall rated; permitted in 1-2 family residential riser applications, or in riser with raceway/fireproof shaft; not permitted in plenums. 

Jacket Rating Substitutions

Rating Description  May be substituted for:  Other ratings that will satisfy the requirement:
CMP  Communications, Plenum  CL3P, CL2P, CATVP, CMR, CL2R, CL3R, CATVR, CM, CMG, CL2, CL3, CATV, CMX, CL2X, CL3X, CATVX  None 
CL3P  Class 3, Plenum  CL2P, CL3R, CL2R, CL3, CL2, CL2X, CL3X  CMP
CL2P  Class 2, Plenum  CL2R, CL2, CL2X  CMP, CL3P 
CMR Communications, Riser  CL3R, CL2R, CATVR, CM, CMG, CL3, CL2, CATV, CMX, CL2X, CL3X, CATVX  CMP
CL3R Class 3, Riser  CL2R, CL3, CL2, CL3X, CL2X  CMP, CL3P, CMR 
CL2R  Class 2, Riser  CL2, CL2X  CMP, CL3P, CMR, CL3R 
CM or CMG Communications CL3, CL2, CATV, CL3X, CL2X, CATVX  CMP, CMR 
CL3  Class 3 CL2, CL3X, CL2X  CMP, CL3P, CMR, CL3R, CM, CMG 
CL2 Class 2 CL2X  CMP, CL3P, CL2P, CMR, CL3R, CL2R, CM, CMG, CL3 
CMX Communications, Residential  CL3X, CL2X, CATV  CMP, CMR, CM, CMG 
CATVX Cable TV, Residential  None CMP, CATVP, CMR, CATVR, CM, CMG, CATV, CMX 
CL3X  Class 3, Residential  CL2X CMP, CL3P, CMR, CL3R, CM, CMG, CL3, CMX 
CL2X Class 2, Residential  None CMP, CL3P, CL2P, CMR, CL3R, CL2R, CM, CMG, CL3, CL2, CMX, CL3X 

This white paper is for informational purposes only and is subject to change without notice. C2G makes no guarantees, either expressed or implied, concerning the accuracy, completeness or reliability of the information found in this document. 

Understand and apply the connectivity set by industry’s standards, specifications, and compliances.