Communications Cable Ratings

The most common terms used to describe communications cables in North America are CM, CMR and CMP. When you see "C" and "M" used as part of a cable's descriptor, it indicates that the cable can be used in accordance with the National Electrical Code (NEC or NFPA 70). In the case of CM, the standard outlines general use, or use in cases where the fire code does not place any restrictions on cable type.

CMR cable, often called "riser-rated cable," is constructed to prevent fires from spreading floor to floor in vertical installations. It can be used when cables need to be run between floors through risers or vertical shafts.

Even higher rated is CMP (plenum-rated cable). This cable is designed to restrict flame propagation to no more than five feet, and to limit the amount of smoke emitted during a fire. This makes it suitable for installation into air plenum spaces, including the space above a suspended ceiling where environmental air can pass through.

In addition to those commonly used terms, we also frequently use other acronyms, such as PVC (polyvinyl chloride) and FEP (fluorinated ethylene polymer). These two terms describe the chemical compounds used in production of the cables. PVC is most often associated with CMR-rated cable; FEP is most often associated with CMP. These terms do not signify any product rating or standards compliance. To maximize cabling performance, it's important to ensure that the type of cable selected meets the standards outlined for your particular project.

Throughout the globe, definitions and acronyms exist to describe similar cable styles surrounding the absence of halogen materials: LSZH, LSOH and LSNH. The terms ZH, 0H, OH, HF, NC, and NH all indicate that the materials used in cable production are free of halogen; LS signifies that low-smoke materials are applied in cable production. 

A rare but emerging cable style uses the term "FR" (such as in FRLS, for example). This indicates that the materials applied to the cable improve reaction to fire (low fire). Most commonly, low-smoke, low-fire, and zero-halogen cables are governed by IEC standards.

A final tip to keep in mind when it comes to cable terms: Learn the distinction between "jacket" and "cable." Often, a job will require that the cable have a certain composition, such as LSOH. If a manufacturer's product data sheet or bulletin calls out an LSOH jacket, however, it's possible that not all materials contained within the cable are LSOH.

At Belden, our network of global manufacturing plants produce many of these common cable styles. Our experts understand the differences in cable ratings, and can help you select the right cable for your project. For more information, please contact your local sales representative or schedule a call with one of our experts!