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Learning The Difference Between Riser, Plenum, and General Application Cable Jackets

Learning The Difference Between Riser, Plenum, and General Application Cable Jackets

There are a variety of characteristics to consider when purchasing cable for an installation, from the conductor gauge to the jacketing material. Cable jackets provide mechanical, fire, chemical, and installation protection to the important inner parts of the cable. The efficiency of their protection is dependent upon the materials the jacket is made of. There are a few different categories of jacketing material, and within those categories there are different fire ratings. The two main, and highest-quality, jacket types are Plenum and Riser, but there is also General Application and Outdoor cable jackets.

What is the Difference Between Riser and Plenum? 

A riser space is a vertical space, like an elevator shaft or wiring closet that spans multi-level floors. Riser spaces are also called non-Plenum spaces. These spaces are required to have no recirculating properties or else they would be considered Plenum Spaces. An example of this is that a Riser space must not be accessible to air conditioning or an HVAC unit.

A plenum space is a space used for air ventilation, like the space in a drop ceiling or anywhere where air is circulating within a building. Because this area delivers air to various parts of buildings, cables running through it need to be made with a high-quality material to prevent the release of toxic smoke. Plenum is made to a higher standard and releases less smoke and toxins than Riser.

What Makes a Cable Jacket Riser Rated? 

Riser jacketed cables are the most common in residential projects and some commercial projects. Cables in Riser spaces stretch between floors, so they contain a strengthening filament with high tensile strength to support the cable as it hangs. Riser cables do prevent the spread of smoke to some extent, but do not limit the release of toxins like the Plenum Jackets. See our collection of  Riser Bulk Ethernet Cable, Fiber Optic Cable, or Coax Cable

What Makes a Cable Jacket Plenum Rated? 

Also referred to as CMP rated jackets, Plenum jackets are made of either low-smoke PVC (Polyvinyl Chloride) or FEP (Fluorinated Ethylene Polymer). These materials offer a higher degree of fire resistance and emit fewer toxins. Because Plenum is the top of the line jacketing, with the highest fire ratings, you can substitute any Riser Cable with a Plenum Cable in a non-Plenum space. But, do not use Riser Cables in Plenum spaces. For a variety of Plenum jacketed cables, check out our CAT5E Ethernet Cables or Armored Fiber Cables. Look at our Networking, Fiber, and Coaxial sections for even more Plenum options!  

What About Fire Alarm Cable?

A fire alarm system is dependent on the quality of the cables used to connect each factor of the network. A fire alarm system can consist of fire alarms, smoke detectors, voice communications, burglar alarms, and so much more. Like networking cables, fire alarm cable has Plenum, Riser, and General Application options. FPL (Fire-Power Limited) is fire alarm cable that is designed to be used for general applications, but not in plenum or riser spaces. FPLR is cable that is meant for vertical runs, like floor to floor or elevator shafts, and has self-extinguishing properties to prevent spreading fire from floor to floor. Finally, FPLP is fire alarm cable that is meant for plenum spaces because it self-extinguishes and produces low toxins and low smoke. Check out our Fire Alarm Cable section for all of our fire cable products! 


Terms to Know

  • *CL/CM/CMG: Refers to the fire rating for general purpose cable jackets. These jackets are not suitable for commercial applications and should not be used in Riser or Plenum spaces.
  • **CMX: Outdoor Application Cables 
  • CMR: Riser Communication Cables.
    • CL3P: Class 3 Riser, commonly used for Commercial purposes
    • CL2P: Class 2 Riser, commonly used for Residential purposes
  • CMP: Plenum Communication Cables.
    • CL3P: Class 3 Plenum, commonly used for Commercial purposes
    • CL2P: Class 2 Plenum, commonly used for Residential purposes
  • FPL: Fire-Power Limited, for general applications.
  • FPLR: Fire-Power Limited-Riser, for use in non-Plenum spaces
  • FPLP: Fire-Power Limited-Plenum, for use in Plenum Spaces

 *General Purpose cables have no fire rating. These are not comparable to Riser or Plenum cable jackets because when General Purpose cables burn they release smoke and toxins, as there are no fire safety aspects to these cables. General Purpose cables are suitable for residential or one-story uses only. 

**Outdoor Application cables, like General Purpose cables, have no fire ratings. Instead, Outdoor Application cables have UV ratings to protect from sun and environmental exposure. Two types of Outdoor Application cables that we carry are Aerial and Direct burial Cables, each with their own specific characteristics. To learn more about these types of cables, read our Outdoor Cable Blog Post. We also offer a variety of Indoor/Outdoor Fiber, Ethernet, and Coaxial cables. 

What Does Your Cable Jacket Say?

If you are ever curious about what cables you have in your home or business just look at your cable jacket! The jacket conveniently tells you all the information you might be looking for, such as the AWG (American Wire Gauge) of your conductor, how many conductors it contains, and the type of jacket it has.

The first section, Manufacturer Name, displays who created the item. Following that is the Standard Rating, which could be a range of different industry standards such as UL, ETL, and RoHS Compliant. After that is the Fire Rating, which can help you determine what applications are suitable for that cable, and if it is Riser or Plenum. On the jacket you can also determine if it is Shielded or Unshielded, what conductor gauge it is designed with, the number of conductors it has, and finally what specified use the cable was created for. 
The exact organization of the jacket labeling may change from product to product, but that is generally the information available. In some cases the jacket will say "Plenum" or "Riser" and in others you will have to look at the fire rating for the "P" or "R" at the end of the specification. Additionally, some cables may list their conductor gauge and count as "Gauge/Count" (16/2 for example means 16AWG, 2 conductors).
Wiring a building is extremely important for networking success and general safety, so make sure you are getting high quality products with the ratings needed for your project! Call Primus Cable today if you have any questions! 
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