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Ethernet Cable: Riser vs Plenum – Which One Is Right for Your Project?

November 21, 2025


When designing a network for a building, choosing the right type of Ethernet cable is crucial—not just for performance, but also for safety and code compliance. Two common fire-rated cables are riser (CMR) and plenum (CMP).

  1. Riser Cable (CMR)
  • Purpose: Designed for vertical runs between floors (in riser shafts).
  • Fire Safety: Slows the spread of fire between floors but emits more smoke than plenum cables.
  • Typical Use: Multi-story office buildings, apartments, or commercial buildings where cables run vertically through walls or riser shafts.
  • Cost: Less expensive than plenum cables.
  1. Plenum Cable (CMP)
  • Purpose: Designed for use in plenum spaces, like air ducts or ceilings, where air circulation is used for heating/cooling.
  • Fire Safety: Highly fire-resistant and emits very low smoke.
  • Typical Use: Ceilings, HVAC ducts, or any area where cable runs through air-handling spaces.
  • Cost: More expensive than riser cables due to higher safety standards.

Which One to Choose?

  • Use riser cable (CMR) for vertical runs between floors.
  • Use plenum cable (CMP) in ceiling or air-handling spaces.
  • Always check your local building codes—they dictate the required fire rating for cables in different parts of the building.

Tip: If your project involves both vertical risers and ceiling runs, you may need a combination of riser and plenum cables for complete compliance and safety.

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