Smart Buildings

Which Rating or Certification Does Your Cable Really Need?

Ron Tellas
Ratings, listings, certifications: These terms are frequently used to indicate how safe a communications cable is, but they’re easy to mix up and can be difficult to understand. How do you know what type of cable rating, listing or certification your project really needs?


Cable safety starts with the National Fire Protection Association (NFPA). For example, you often see cables labeled with “CMP,” “CMR” and “CM” descriptors. These are listings defined by the NFPA in Article 800.179. Seeing “C” and “M” together in a cable’s descriptor indicates that the cable can be used in accordance with NFPA 70 (also known as the National Electrical Code [NEC]). “CM” indicates a cable for general use (with the exception of risers and plenums) and is listed as being resistant to the spread of fire.


A “CMR” cable (riser-rated cable) is a cable listed as having fire-resistant characteristics to prevent fire from spreading between floors in vertical installations. This descriptor indicates that the cable can safely run between floors through risers or vertical shafts.


 A “CMP” cable (plenum-rated cable) is a cable listed as having adequate fire-resistant and low smoke-producing characteristics, such as restricting flame propagation to five feet or less and limiting the optical density of smoke produced during a fire. This descriptor indicates that the cable is suitable for installation in ducts, plenums and other spaces that circulate environmental air within buildings, such as raised floors or spaces above suspended ceilings.


How Do I Know What I Need?


So how do you know what type of safety certification, listing or rating your cable needs?


The type of space you’re working with determines what your local authority having jurisdiction (AHJ) will require in terms of a listing in order to comply with NFPA codes.


Today, the requirements necessary to comply with a listing are regulated through certifications. Once you know how the space should be listed, then you need to find a product certified to that listing. Certification is granted through an OSHA-authorized Nationally Recognized Testing Laboratory (NRTL).


Many people in our industry don’t realize there are several NRTLs that can perform tests and grant certification to products that meet construction requirements and OSHA safety standards.


Some NRTLs you may recognize include:


  • CSA Group Testing & Certification Inc.
  • FM Approvals
  • Intertek Testing Services (ETL)
  • NSF International
  • Southwest Research Institute
  • TÜV Rheinland of North America Inc.
  • Underwriters Laboratories Inc. (UL)


Each NRTL is approved to certify products to certain industry standards, and each NRTL uses a unique registered certification mark that certifies a product’s conformance to applicable product safety test standards.


After a product is certified or rated by an NRTL, then that same NRTL permits the manufacturer to place a registered certification mark on the product. This indicates that the NRTL tested and certified the product for compliance.


Not all cables require the same certifications from the same NRTLs. The product certifications you need for your project are based solely on how and where the cable will be used.


Finally, you must make sure that your local AHJ—whether it’s the fire marshal, electrical inspector or building official—accepts the product as compliant. Remember: The AHJ has final say in whether you’ve met the necessary requirements or not. 


Where Do I Start?


We’ve seen many people start too far forward in the process. Instead of first trying to determine the product certification you need, take a step back and consider your application and space. That will determine the listing requirements. From there, you can look for a product certified to that specific listing.



For example, don’t start your project by looking for a cable that’s ETL or UL rated. Instead, consider the bigger picture. If the cable is going into a plenum space, for example, then you need to make sure first and foremost that it’s CMP certified and listed for use in a plenum space. Don’t just look for the NRTL mark; the product may be certified for other purposes. Always ask for proof of compliance from the manufacturer. 


To put it simply: Worry less about ratings and certifications upfront. Instead, focus on:


  1. Identifying the listing that matches your space
  2. Identifying the certification your product needs in order to match that listing
  3. Pinpointing a product with that proper certification
  4. Obtaining proof of compliance


Let’s consider cable for a plenum space as an example. First, you need to identify the listing that matches the space. Then you want to find a product that’s certified to pass the requirements for a plenum space to ensure safety. That certification for a CMP-rated cable comes from an NRTL.


This can be a complicated topic to understand. Do you still have questions about cable ratings, listings and certifications? Send me a note. I’m happy to help you wade through it.