When we refer to cable as plenum or non-plenum we are not talking about the cable itself. The plenum rating that we are talking about actually refers to the jacket that surrounds the cable. There are two basic types of building construction as it regards the movement of heating, air conditioning and ventilation through office buildings.
Typically, spaces between the structural floor or a dropped ceiling are considered plenum. Some drop ceilings are actually designed tight enough to where air circulation is restricted and may be considered a non-plenum area. As far as cost savings, non-plenum cable is usually close to half the price, if not more, than PVC jacketed cable. Many projects will use non-plenum cabling to save on costs; however, it is ultimately up to the building owner or the goverment codes and regulations on whether or not to use plenum vs.
Insurance issues may also have an impact on the chose of plenum vs. Flame-retardant, low smoke materials such as polyvinyl chloride PVC , fluorinated ethylene polymer FEP , or a polyolefin offer good resistance against fire, and in the event that they do begin to burn, they will not emit large quantities of harmful fumes.
Which is a win-win! Why is this all necessary? Since plenum cables are routed through air circulation spaces which often contain very few fire barriers , they need to be coated in material that won't contribute to the spreading of flames. Also, as network and communications cabling runs typically spread throughout buildings to make sure everyone is connected to everyone else , having them ignite would be a surefire no pun intended way for the flames and smoke to spread that much quicker.
So seriously, this is not the place you want to cut corners. Now, perhaps you've also heard of a thing called riser cables. You might have heard that these are also flame retardant, so maybe you think you can get away with using riser cables in plenum spaces. Riser cables are intended for non-plenum, vertical applications ie. They typically incorporate load-bearing strengtheners since they need to stay upright without being stressed too hard, and it's true that they do have to be fire resistant.
While you can use plenum cables in riser applications, the opposite is definitely not true. Bottom line? If your cabling application requires materials that are flame-retardant or compliant with strict safety standards, always opt for plenum-rated products.
As it happens, CableOrganizer. Need help? What is the difference between male and female connectors? What is the difference between 75 Ohm and 50 Ohm coaxial cable and when should each one be used? What are some popular Fiber Optic connector types?
Why Use Shielded Cat 6 Cable vs. Unshielded Cat 6 cable? Is your website secure? How do I return a purchase? What are your shipping and processing fees? Plenum rated CMP cable has an outer jacket made of fire-resistant material like Teflon to prevent fire from spreading.
Some residential buildings are never inspected. Depending on your jurisdiction, you may need to simply show that your cable is plenum-rated. In some stricter jurisdictions, you may need to show that the cable is UL listed as well. The following cables meet plenum-rating specifications, but are not UL listed:. UL-listed cable should generally be marked with the UL trademark marking and approval number, which you can use to look up the cable online for free.
Non-plenum cables can be used anywhere except plenum space and air ducts. In both commercial and residential buildings, non-plenum cable can be used to run cables through walls and across open ceilings. You must use CMR riser-rated cable when running cable between floors through risers or vertical shafts.
Some buildings with HVAC systems have return air ducts which transport air back outdoors. If there are no leakages and the space above a drop ceiling is not circulating air, you may use non-plenum cable.
Of course, this is only true as long as the cable is not running inside the air ducts themselves. Non-circulating plenum airspace may become active due to disconnected ductwork. But, before you go ahead, check with your insurance provider and local area building code. Some insurance providers and building codes require plenum cable even for non-plenum spaces depending on factors like building height, purpose and occupancy.
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