Plenum vs. Riser
Plenum (CMP) Rated Cable
Complies with NFPA-262 and UL-910. Only cable allowed in spaces defined as air plenums such as raised flooring systems and air handling ducts. Plenum cables must self extinguish and not reignite. They also produce less smoke than traditional PVC cables. The smoke and fumes are toxic.
Riser (CMR) Rated Cable
Comples with UL-1666. Defined for usage in vertical tray applications such as cable runs between floors through cable risers or in elevator shafts. These spaces cannot be used for environmental air. These cables must self extinguish and must also prvent the flame from traveling up the cable in a vertical burn test.
Other Cable Ratings:
Low Smoke Zero Halogen (LSZH) Rated Cable
Used in shipboard applications and computer networking rooms where toxic or acidic smoke and fumes can injure people and/or equipment. Examples of Halogens include Fluorine, Chlorine, Bromine, and Iodine. These materials when burned produce acidic smoke that can harm people and computer equipment. Low Smoke means the cable does not produce the heavy black soot and smoke common with PVC cables. These cables will self extinguish but cannot pass UL-910 or UL-1666 for a plenum or riser rating.
General Purpose (CM, CMG, CMx) Cable
Complies with UL-1581 testing. Will burn and partially self extinguish. Not for use between build floors or in air plenum spaces. Often these cables are used for workstation cables and patch cords.