We get this question asked from time to time and decided to add it to our blog.
Although Plenum rated cable CMP and Riser Rated cable CMR have similar in characteristics, like both being low voltage and power limited, here is where they differ.
Plenum Cables are manufactured with low smoke insulation materials such as FEP Fluorinated Ethylene Propylene, Fluoropolymer FCP and Low Smoke PVC for the sole purpose to reduce smoke and flame emissions in case of a fire. These must adhere to flame tests requirements from agencies like UL, ETL, National Fire Protection and the National Electrical Code (NEC 725, NEC 800). The most popular Plenum cable ratings are, CMP, CL3P, CL3P, FPLP, MPP and CATVP. Plenum cables are usually installed by electrical and HVAC professionals in the air conditioner return air ducts of a building.
Here are a few examples of Plenum Rated Cable:
Plenum Cable 22 AWG Gauge
Plenum Cable 20 AWG Gauge
Plenum Cable 18 AWG Gauge
Plenum Cable 16 AWG Gauge
Plenum Cable 14 AWG Gauge
Plenum Cable 12 AWG Gauge
Plenum Cable 10 AWG Gauge
Riser Rated Cable is manufactured with a low flame vertical spread factor, in other words, to prevent flames from traveling upwards and rising between floors of a structure. These cables are made with riser rated PVC Polyvinyl Chloride. Riser Rated cables are not approved for use in plenum areas the same way plenum cables are because they do not have the low smoke properties that are present in plenum cables. Riser cables are installed by cabling installation professionals and carry a cable rating of CMR, CL3R, CL2R and FPLR.