Communication Cable Jacket Ratings

Which type of cable jacket should you choose? What’s the difference between CM, CMR, CMP, and other cable jackets? And which one should you use for your network?

There are two key facts that we need to understand about cable jackets. First, they protect our cables against moisture, mechanical, flame, or chemical damage, meaning they don’t have any bearing on the inner workings or transfer speed.

Second, we sort cable jackets according to their ability to resist fire and, as a result, we’ll use different ratings in different places. All these jacket types come from the National Electric Code, which is published by the National Fire Protection Agency.

Essentially, the highest-grade cable jackets offer the most fire resistance and are suitable for specific locations. That’s why an optimal approach combines various cables at different locations to create a safer environment.

So, let’s dive into our cable jacket ratings.

CM/CMG

Short for Communications Multipurpose or Communications Multipurpose General, this cable jacket is the most commonly used in residences, single-story commercial buildings, or to make any other connections within a single room. These cables are made from vinyl, otherwise known as PVC (polyvinyl chloride) and have passed “vertical tray flame test,” meaning that they don’t ordinarily spread flames more than eight feet.

CM/CMG cables are suitable for installation in cable trays and other non-plenum/non-riser areas.

CMR

The next tier up is Communications Multipurpose Cable, Riser, or riser-rated cables. These jackets are made to prevent fires from spreading between floors through vertical shafts or risers. By adding a Teflon coating or baking strands of fiber into the jackets, this product limits the cable’s ability to carry flames and makes them suitable for in-wall installations.

Riser rated cables are designed to run vertically from floor to floor in non-plenum areas.

CMP

Otherwise known as Plenum-Rated Cables, CMP jackets are the most flame retardant of the bunch, and they are constructed to limit the amount of smoke emitted in case of a fire and prevent flames from spreading more than five feet. This makes CMP cables suitable from installation into air plenum spaces, including the space above a suspending ceiling or the raised floor where environmental air can pass through. These spaces require stricter fire safety mandates because the plenum area is highly conducive to spreading fire and smoke throughout a building.

CMP Plenum cables are necessary in plenum spaces because they offer the superior fire resistance that we need to ensure safety in our buildings.

CMX

The last type of jacket type is CMX, or outdoor cables that are suitable for direct burial or open air. These jackets typically use LLDPE (Linear Low Density Polyethylene) instead of PVC because it is UV resistant and weather-proof which are recommended for outdoor use.

CMX cables are intended for use in buildings where the cable is enclosed in a non-combustible conduit or be used for outdoor runs.

Comtop Bulk Ethernet Cables

Whether you’re looking for CMG, CMR, CMP, or CMX cables, Comtop provides a variety of high-quality Ethernet cables for all different use cases. The following chart is a great reference for you to easily review some of our offerings.

If you need to get a quote for our Ethernet cables or other connectivity solutions, please call us at 1-909-597-0883.