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Understanding Plenum and Other NEC Cable Ratings

Cables are an essential part of electrical projects, and it’s important to understand the ratings and features of different types of cables. Let’s look at plenum cable and other NEC cable ratings and what they mean for your project.


If you are going to build a firm or a commercial space for your business, you should know the purpose of a plenum space. This is an open space above your ceiling or under your floorings. Every building has a plenum space where cables for the WIFI network, signal booster, antenna system, and other HVAC system cables that connect throughout the whole place are usually located.

Plenum spaces are rooms for breathable air that circulates the whole place. With its rapid amount of oxygen, possible fire threats can happen instantly and compromise the plastic cables attached. This is why installing flame retardant plenum cables is necessary to prevent the rapid spread of fire. This is a method we call plenum rated and should be strictly observed for any building or residential project. 

Due to the open-space characteristics of a plenum, workers should secure the airways in every duct system to ensure that when a fire is formed, no fumes or smoke will rush quickly throughout the whole building.


Have you seen a thick, fiery smoke coming from your plenum spaces? Often, fire outrage in your plenum spaces can be quickly enraged by the plastic cable wires attached. These unrated plenum cables can be the source of further fire damage and will bring extra danger to the entire occupants of the building. This is why getting a plenum-rated cable for your plenum spaces either above the ceiling or underneath the floorings is still a smart decision to prevent any possible fire threat. 

A plenum cable is a type of low-smoke, zero-halogen cable. This cable type is often used in commercial and institutional settings where safety is a top priority. The cables are designed to emit little smoke and no toxic fumes if they ever catch on fire. This makes them ideal for use in areas where people may be present, such as schools, hospitals, or office buildings.

Plenum cables are usually coated with a PVC “polyvinyl chloride” material or FEP “fluorinated ethylene polymer” coating jackets which serve as fire barriers or covers that hinder the spread of flames from one place to another. It also prevents the release of hazardous smoke fumes caused by the burning plastic cables. 

Standard plenum cables are coated with a Teflon-coated wire, considered flame and heat resistant. This is primarily observed during cable wiring installation for home and network communication systems. Moreover, plenum cables are considered the safest and the highest standard option, which suits various cable types. 

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Basically, fifteen NEC guidelines should be observed in every building project. But there are three major communications multipurpose (CM) that are common to electricians. These are the following:

Plenum Rated (CMP) Cable

This multipurpose communication standard has the highest fire-resistance rating among the other cable ratings. This type is usually made from low-smoke PVC or FEP compound materials, hindering high-level smoke and flames from spreading quickly into the plenum space. As a result, CMP cables are the perfect plenum cables for air ducts and plenum spaces. Although they are pretty expensive, the quality of service they can provide is immeasurable. 

Riser Rated (CMR) Cable

Compared to CMP cables, this plenum cable type has a medium fire resistance that can still control fire outrage in your plenum space. It is usually used in risers and sometimes called PVC cables due to the PVC compound which is used on its jackets. 

Standard (CM) Cable

This type of plenum cable is usually applied to patch cords and jumpers. Standard cables are used only if there are no further restrictions on the cable type concerning the fire code. Also, these types of cables can be installed through your building walls and underneath your flooring area. 


Now, the question left here is, who will take charge of the cable ratings? Who are qualified to perform cable ratings on our plenum spaces?

For the enforcement and implication of standard code requirements regarding the safety and protection of plenum spaces and other fire hazard concerns, the National Fire Protection Association (NFPA) is in charge and authorized to operate in this matter. 

When it comes to the safe installation of electrical wirings, cables, and equipment, the NEC or the National Electric Code office is responsible for all these matters. They also set the standard guidelines for electrical safety in various industrial, commercial, or residential buildings. 

The National Recognized Testing Laboratory (NRTL) works with the National Electric Code (NEC) to decide on compatibility and provide certification that shows clear evidence of compiled requirements on electrical and electronic equipment.

For cable testing, the Underwriter Laboratories (UL) are the one setting the standard for cable requirements and checks if you have exceeded or completely complied with the set guidelines. They are responsible for the testing process on plenum cables. They can provide certification to factories that made the electronic products and attach a UL official number plus their trademark.

Regarding safety precautions on cable installations, do not settle for less-mediocre services. Always trust the best and high-quality works from certified companies. If you are looking for cable distributors to help you with cable works, call the experts at Tevelec, the leading wire and cable distributor for decades.

We have specialized expert services for specific projects that our clients need. Call us today! 

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