According to Underwriters Laboratories (UL), a regulating agency for cable management products, there are three different types of cable raceways — plenum, risers and general purpose. It is helpful to know the differences between them when shopping for wire management products.

  • A raceway marked “plenum” is for use in ducts, plenums or other spaces used for environmental air when used to enclose optical fiber cables marked OFNP or communications cable marked CMP or CMP-OF. Plenum is a space, in a building, between the real ceiling and the dropped roof often used as an air duct for heating and air conditioning. It is also filled with electrical, telephone and network wires. Plenum raceways use a fire retardant coating that must comply with local building codes.
  • A raceway marked “riser” is suitable for installation in risers when used to enclose optical fiber cable marked OFNP and OFNR or marketing communications cable marked CMP, CMP-OF, CMR or CMR-OF.
  • A raceway with neither the marking “plenum” nor “riser” is ideal for general purpose use.