What is CM/CMR/CMP?

 Among all these terms, CM, CMR, and CMP are the most common Ethernet cable ratings specified by the National Electric Code (NEC). They’re named by the ability to resist to fire to ensure safety in case that you didn’t use the right cable rated for its intended use.

the ability to resist to fire: CM<CMR<CMP. PVC is the material that makes up the Ethernet cable jackets with CM, CMR, and CMP ratings. That’s why we can often see Ethernet cables are labeled PVC CM, PVC CMR, or PVC CMP on the jackets. 

CM stands for “Communications Multipurpose”. These are the types of cables that you usually see running from your computer to switch or wall port. These cables are most known as patch cords and come in the stranded form. Stranded cm cables give them greater flexibility for the purpose of connecting short runs to your personal computer to server racks.

CMR cable stands for "Communications Multipurpose Cable, Riser". These ones are more used to riser applications, hence the name, and are less used for patch cables. This means that they are usually run along bottoms or tops of walls and from the basement to the upper floor, so long as the cable does not need to run through an air duct. 

CMP cable stands for "Communications Multipurpose Cable, Plenum" CMP is used for networking that must be done in air ducts or vents. Typically, CMP is used for offices or homes. For the latter, it is a practical application if the home network must be wired through ducts.

Each different type is used in different locations.

CM is the most basic cable jacket rated for general use. CMP is higher rated than CMR. The most significant difference is that they are suitable for different situations with various types of airspace. Both CM and CMR cable jacket is made from the relatively inexpensive polyvinyl chloride (PVC). Price and flexibility are the upsides of PVC, but the PVC material can release thick smoke and dangerous gases like hydrogen chloride in a fire. While CMP cable jacket is made from either a low-smoke polyvinyl chloride (PVC) or a fluorinated ethylene polymer (FEP). Since the jacket material requirement for CMP is stricter than that of CM and CMR, their fire resistance and application ranges are different. CM cables for general use can not replace CMR and CMP cables but both CMP and CMR Ethernet cables can be institutes of CM Ethernet cables. Ethernet cables with CMP jacket can always replace cables with CMR jacket, but CMR cable cannot replace CMP cable in plenum spaces.

If you want to know more details, you can contact me by email-sales6@adtek-fiber.com

Reference：

1."Ethernet Cable Jacket Ratings: CM vs. CMR vs. CMP"

2."What's the difference between CM, CMR, and CMP?"