What Is The Difference Between Pvc And Plenum Cabling?
There’s no telecommunication difference (e.g. noise, crimping, termination), just the sheathing. The difference is an electrical code safety issue.
Regular network cable (i.e. non-plenum) is flammable, can catch fire, can spread fire, and emit toxic fumes when burning.
Plenum quality cable is required for use if you run your cable in air handling spaces (i.e. air ducts), or if you’re running them between floors. Plenum cable is fire-resistant (it will melt, but not support combustion or carry a flame). It also emits less toxic fumes when it does burn.
If you look at some network cable, you can see which type it is:
CMP: Plenum rated cable (plenum means “air handling space“)
CMR: Riser rated cable (riser means “between floors“)
LSZH: Low smoke zero halogen rated cable
CM/CMG/CMx: General purpose cable
PVC: Unrated cable
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, Bromin
e, 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 cannotpass 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.
LSZH And PVC Cables
The European market is demanding that cables used in LANs, WANs, etc. meet LSZH specification. The IEC 60332-1 governs the Flame Retardant Grade specifications in reference to LSZH cables.
Reduction of dangerous/poisonous gases
Essentially, the compound used in manufacturing cables meeting the above specification reduces the amount of dangerous/poisonous gases in case of fire. The main difference in specifications between IEC 60332-1 versus UL® 1581, UL 1666 and UL 910 is that the cable under the IEC spec can continue to burn while still emitting very low gases. The UL specs demand that the flame be extinguished, but it can still emit dangerous/poisonous gases.
Today virtually all medium and large installations in Europe must meet the IEC specification. Many public authorities are already demanding that new installations must meet IEC 60332-3 which is a more demanding flammability specification for LSZH.
What’s the difference between PVC and LSZH cables
Physically, PVC and LSZH are very different. PVC patchcords are very soft; LSZH patchcords are more rigid because they contain the flame retardant compound, and they are aesthetically more pleasing
A PVC cable (made of polyvinyl chloride) has a jacket that gives off heavy black smoke, hydrochloric acid, and other toxic gases when it burns. Low Smoke Zero Halogen (LSZH) cable has a flame-resistant jacket that doesn’t emit toxic fumes even if it burns.
LSZH more expensive and less flexible
LSZH cables usually cost more than the equivalent PVC cable, and certain types are less flexible. LSZH cable does have some restrictions. According to CENELEC standards EN50167, 50168, 50169, screened cables must be halogen free. However, no similar regulation yet applies to unscreened cables.
Where do you run the cable?
Whether you choose a riser (PVC), plenum or LSZH jacket depends on where you’re going to run the cable.
PVC cable is commonly used for horizontal runs from the wiring centre. You can use it for vertical runs between the floors – but only if the building features a contained ventilation system running through the duct work.
LSZH cable is used between floors in a building. It has a special flame-retardant coating.
A plenum is a space within the building created by building components, designed for the movement of environmental air.