Plenum Cable Explained


Plenum Cable Explained 

In the vast lexicon of network cable installation, you have probably run across the term plenum in your research- often shorthanded by the acronym CMP. So, what is Plenum Rated or CMP cable? When and where do you need to use it? Why exactly is plenum required for certain projects but not others? If you find yourself needing to utilize Plenum rated Ethernet cable in your network cabling installation projects, as many contractors do, you have come to the right place to both learn about it and stock up on it.

What is Plenum Cable?

Let’s start with the most basic plenum definition; Plenum is a designation that indicates a cable is rated with low smoke and low flame elements by means of specialized insulation. The abbreviation CMP simply stands for “Communications Plenum”. In comparison to standard network cabling, plenum cable is far more flame retardant and insulated with jacketing materials that are less toxic when exposed to high heat and flame. Many US building and fire codes require plenum rated cable be used in installations that necessitate wiring be run through “Plenum Space”.

Where do I need to use Plenum rated cables?

Before determining if a plenum ethernet cable is the right cable for your installation project, it’s essential to understand what is considered a “Plenum space”. In its most basic definition, Plenum spaces are designated areas in a building that facilitate return airflow circulation for HVAC systems. Some examples of plenum space include the areas between dropped and structural ceilings and the space beneath raised and structural flooring. Ductwork is also technically considered plenum space. Basically, any enclosed conduit or area through which air is flowing can be considered plenum space or plenum conduit.

First, check your local building codes or the institution to whom you are contracted. If plenum rated patch cable is a requirement for a network installation project, that designation is sure to be listed and clearly outlined. School buildings, government facilities, and hospital installations almost always require plenum rated patch cable for large networking projects- specifically between floors and in plenum ceiling areas. Of course, CMP rated cable can be used in non-plenum spaces, as well.

What exactly makes Plenum different?

Most standard non-plenum cable jacketing is made from PVC- polyvinyl chloride. While it is a durable and cost-effective material that is ideal for most applications, if it were to catch fire or smolder, PVC emits toxic fumes into the atmosphere. Being that Plenum spaces functionally exist to facilitate air circulation, it’s essential to ensure said toxic fumes do not spread throughout the building by way of these areas.

By nature, HVAC equipment and duct work enable increased levels of oxygen flow- obviously much more so than non-plenum areas. Oxygen- being a key component in fire proliferation- forced through these areas, will cause a fire to spread at rapid speeds through plenum areas and ducts. Even a small smolder can become a raging flame when exposed to the increased airflow rate in plenum areas. As a result, fumes created by anything burning in these areas will quickly be distributed through the building, creating an even more dangerous environment for occupants as they attempt to evacuate.

To follow commercial health and safety standards in certain industries, it is required by law to use Plenum rated Ethernet cable in such spaces. School buildings are one of the many institutions that must ensure these modern cabling requirements be adhered to for the safety of the occupants..

Who sets the regulations regarding plenum cables?

The National Fire Protection Agency (NFPA) is the institution in charge of dictating general fire safety building codes- including protective requirements for plenum air spaces. NEC (National Electric Code) is their published standard that outlines cable ratings and installation guidelines. Delineated in Section 800 of the NEC are the requirements necessary for network and AV cabling to be considered compliant. Underwriter Laboratories certify items and manufacturers who meet these standards.

Our bulk plenum cable supplier is Vertical Cable- a UL certified and widely trusted brand. You can rest assured that any Plenum- CAT5e patch cables, CAT6 patch cables, and bulk – purchased through Cables for Less is a quality product guaranteed to meet the highest industry NFPA safety standards. View a spec sheet here to see for yourself.

What about Riser Rated Cables?

Surely you have also run across the Acronym “CMR” in your research. In short, CMR stands for Communications Riser Cable. Riser cable or CMR cable is simply an NEC designation that indicates the cable is approved for use in riser spaces- ie vertical areas between floors. It’s quite important to understand the differences in plenum and riser cables before starting your installation project. All plenum is riser rated, but not all riser rated cables are plenum. Riser cable cannot be used in place of plenum- but plenum can be used for riser applications. Be sure to double check the NFPA requirements for your project before purchasing CMR if you are working in a plenum space.

Where can I buy plenum cables?

We offer a large selection of various colours of bulk CMP cable in CAT5, CAT6, and CAT6a sure to satisfy all your project requirements, no matter how specific.

To create your own custom plenum patch cable runs, check out our wide variety of bulk stock in easy to use 1k foot pull boxes. Simply pull what you need, cut to length, and go. The remaining cable stays neatly coiled in the box ready for the next run- no tangling or mess to deal with. You’ll also need compatible connectors, cutting & crimping tools, and testing equipment.

Don’t want to deal with the hassle of constructing the cables yourself? Totally understandable! Let our highly trained staff with over 15 years of experience in the fabrication industry take care of that part for you. Our custom Plenum patch cables are made right here in the Midwest with the highest level of care and quality materials. We offer plenty of CAT5e standard stock lengths in white, as well as the option to completely tailor your CMP runs with our handy custom cable calculators. Our CAT5e and CAT6 plenum patch cable calculators give you the option to customize your connectors, pin-outs, cable colours, and lengths.


In closing…

When it comes to plenum rated patch cables, Cables for Less has got you covered. If you have any questions, please don’t hesitate to call and speak to one of our knowledgeable, friendly staff members to get an order placed today! We are standing by to help and look forward to speaking with you!

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