CMP stands for Communications Plenum Cable, a type of communication cable rated for use in air-handling spaces, known as plenums, within commercial and industrial buildings.
CMP cables are designed to meet the most stringent fire-resistance and smoke-production standards required by building safety codes. These cables are used in plenum spaces, which are areas above drop ceilings or below raised floors that facilitate air circulation for heating, ventilation, and air conditioning (HVAC) systems. Because these spaces can rapidly circulate air during a fire, any materials placed in them must have limited flame spread and produce minimal smoke. CMP-rated cables are manufactured using flame-retardant and low-smoke materials, such as fluorinated ethylene propylene (FEP) or low-smoke PVC compounds, which allow them to meet these strict performance requirements.
The CMP rating ensures that a cable will not contribute significantly to the propagation of fire or the production of toxic smoke, thereby protecting both people and equipment in commercial facilities. In the structured cabling industry, CMP cables are often used for data, communication, audio-visual, and control systems, especially in environments that prioritize fire safety and compliance. While CMP cables are more costly than riser (CMR) or general-purpose (CM) cables due to their specialized construction, their use is critical for maintaining safety and adhering to local and national codes.
CMP cable ratings are governed by the National Electrical Code (NEC) under Article 800, with performance standards established by Underwriters Laboratories (UL). UL 910 (NFPA 262) is the defining test for plenum-rated cables, measuring both flame spread and smoke density.
The development of CMP cables became essential after building codes began emphasizing fire safety in the 1970s and 1980s, particularly following studies showing that toxic smoke, not flame, was often the leading cause of fatalities in building fires. Advances in fluoropolymer insulation and jacket compounds allowed cable manufacturers to meet these elevated standards, leading to the widespread adoption of CMP-rated cables across the commercial and industrial sectors.