Plenum Cable vs Non-plenum Cable

When building a copper cabling system for office or home, one constant that seems to be always taken into consideration is plenum cable vs non-plenum cable, which one does the project actually need? Plenum and non-plenum refer to the jacket that surrounds the cable, which is defined by NEC (National Electric Code) aiming at preventing the fire spread and toxic smoke in buildings. Then, how to make a wise choice between plenum cables and non-plenum cable? This article first introduces plenum Ethernet cable and non-plenum network cable, then explains how to make a choice.

Plenum Cable Explanation

Plenum is a separate space provided for air circulation for heating, ventilation, and air-conditioning (also referred to as HVAC), which is the space between the structural ceiling and a drop-down ceiling. And it may also be under a raised floor. Plenum cable is also called CMP (Communications Multipurpose Cable, Plenum) for short, which is the cable that is laid in the plenum spaces of buildings. This cable is made from less hazardous and lower smoke materials than non-plenum cables, which is approved by UL (Underwriters’ Laboratories) for non-conduit applications located in environmental air spaces. The cable is designed to restrict flame propagation and limit the amount of smoke. Compared with the traditional PVC cable, plenum cable produces less smoke. Thus, plenum cable is suitable for installation into air plenum spaces, especially in the locations like schools and hospitals for safety concerns.

Non-plenum Cable Explanation

Non-plenum cable usually serves to run through non-air circulating areas. Non-plenum includes riser rated cable, and other rated cables like CM cable, etc.

Riser rated cable is also called CMR (Communications Multipurpose Cable, Riser) cable. It’s constructed to prevent fires from spreading floor to floor in vertical installations. The fire rating of riser cable is not as strict as the plenum cable since plenum cable uses less hazardous and lower smoke materials. This means CMR cable will exhibit more smoke than CMP cable. Thus, plenum cable can replace riser cable, but not the other way around. And the price of riser cable is less than plenum cable. Usually, the cable can be deployed to run between floors through risers or vertical shafts.

CM cable is the cable used for communication applications like Ethernet. This cable has passed “vertical tray flame test”. Typically, CM cable is applied for workstation cables and patch cords, connecting the network switches, servers, PoE devices and so on, but not for use across the floors or in air plenum spaces.

Which to Choose?

Plenum and non-plenum cables are designed with different flame ratings for different applications as the figure shows.

Plenum cables have the strictest flame ratings with higher cost, since they have a special coating on the wire. They are usually used in plenum spaces for preventing flame spreading and reduce the smoke amount. But during the installation, plenum cables tend to be a little more difficult to install because sometimes it may “kink” more readily. This cable type can be used in commercial and residential area or hospitals, since these areas are crowded that safety must come first.

For non-plenum cables, the riser cables can be used in the risers of commercial buildings, with lower cost than the CMP cables. Note that, CMP cables also can be used in the vertical telecommunications infrastructure if one has enough budget, because there’s no telecommunication difference (such as noise, crimping, termination) between CMP and CMR cables. For example, plenum rated Cat6 and riser rated Cat6 perform the same in the data transmission. As for the CM cables, they are usually the common Ethernet patch cables, which is the lowest cost with easy installation. They are designed for general use, which is widely deployed to connect networking devices like servers, network switch, routers and so on. Therefore, customers need to choose plenum and non-plenum cable based on actual demand and budget.

Where to Buy Plenum and Non-plenum Cables?

Both plenum and non-plenum cables are available at FOCC. FOCC offers Cat6 plenum cable. This UTP bulk network cable uses solid Oxygen-free copper, which is rated for any 10/100/1000Base-T networks and meets PoE/PoE+ standards for PoE applications. FOCC also offers Cat5e/Cat6/Cat6a/Cat7 CMR bulk Ethernet cables that are available in UTP and STP. These Ethernet cables are designed with low resistance for better transmission performance. Plus, FOCC provides 24AWG and 28AWG copper cables. These network cables use PVC CM cable jacket while some other providers use PVC. This means FOCC Ethernet cables have better fire resistance, and can operate in the temperature from -20 to 60°C. All the common copper patch cables have passed the Fluke Channel Test to ensure superior transmission performance. All the plenum cable, riser cable and common Ethernet cables at FOCC adopt Oxygen-free copper design, which brings higher electric conductivity, and reduces signal loss.

Plenum vs. Non-Plenum (Riser) Rated Fiber Optic Cable

Overview: Understanding the distinction between Plenum (CMP/OFNP) and Non-Plenum (Riser/CMR) rated fiber optic cable is critical for network safety, performance, and compliance with the National Electrical Code (NEC). Plenum cables are engineered with superior fire-retardant, low-smoke jacket materials for safe use in air-handling spaces (plenums), while Riser cables are designed to prevent fire spread vertically between floors in non-plenum shafts. As a direct manufacturer, we supply both types to meet specific building code requirements for B2B clients.

Benefits & Applications

Plenum (CMP) rated cables are mandatory for installation in horizontal runs within air handling spaces, such as drop ceilings and raised floors, common in commercial buildings, hospitals, and data centers, due to their low smoke and flame propagation characteristics. Non-Plenum Riser (CMR) cables offer a cost-effective and compliant solution for vertical installations in building shafts and cable trays that connect different floors, where the fire-resistance requirements are less stringent than in plenum airspaces.

Key Technical Benefits

Plenum (CMP/OFNP) Cable:
– Superior fire resistance and minimal flame spread
– Low-smoke PVC or FEP jacket materials minimize toxic fume emission
– Complies with stringent NFPA 262 (Steiner Tunnel Test)
– Mandatory for use in ducts, plenums, and other air-handling spaces
– Higher temperature tolerance for demanding environments

Riser (CMR/OFNR) Cable:
– Designed to prevent the spread of fire vertically between floors
– Complies with UL 1666 (Riser Flame Test)
– More economical choice for non-plenum vertical installations
– Standard fire-retardant PVC jacket construction
– Ideal for runs in building risers and elevator shafts

Technical Specifications

As a direct factory manufacturer and wholesale supplier, we offer competitive factory pricing on both Plenum (CMP) and Riser (CMR) rated bulk fiber optic cables. We provide full OEM branding and customization for bulk orders, enabling you to procure code-compliant cabling directly from the source.

FAQ

1. What is the main difference between a Plenum rated cable and a Riser rated cable?

The primary difference between a Plenum (CMP/OFNP) rated cable and a Riser (CMR/OFNR) rated cable is their fire resistance and smoke emission. Plenum cables have a more fire-retardant jacket that emits less toxic smoke, making them safe for air-handling spaces, whereas Riser cables are designed only to prevent fire from spreading vertically between floors.

2. Can I use a Riser (CMR) fiber cable in a plenum space?

No, you cannot use a Riser (CMR) fiber cable in a plenum space. This is a violation of the National Electrical Code (NEC) and poses a significant fire safety hazard, as CMR jackets do not meet the stringent low-smoke and flame-spread requirements for air-handling areas.

3. Is it acceptable to use a Plenum (CMP) fiber cable in a riser application?

Yes, it is acceptable to use a Plenum (CMP) rated fiber cable in a riser application. Plenum cables have superior fire ratings that exceed the requirements for riser spaces. While compliant, using a CMP cable where a CMR cable would suffice is often not cost-effective.

4. How can I identify an OFNP (Optical Fiber Nonconductive Plenum) cable?

You can identify an OFNP cable by the markings printed on its outer jacket. The jacket will be clearly labeled with “OFNP” or “CMP” to indicate its plenum rating, ensuring compliance with fire codes.

5. Why are plenum fiber optic cables more expensive than non-plenum versions?

Plenum fiber optic cables are more expensive because their jackets are made from higher-grade, specialized materials like FEP or low-smoke PVC. These materials have superior fire-retardant properties and are more costly to produce than the standard PVC used for non-plenum riser cables.

6. What does the NEC say about using OFNR (Optical Fiber Nonconductive Riser) cables?

The NEC permits OFNR cables to be used in vertical runs penetrating floors, such as in building risers or elevator shafts. They are specifically tested to prevent the spread of fire from one floor to another but are not permitted in plenum air-handling spaces.

7. As a wholesale buyer, which fire rating should I stock the most?

As a wholesale buyer, it is wise to stock both Plenum (CMP/OFNP) and Riser (CMR/OFNR) cables. However, Riser-rated cable is often used in a wider variety of general-purpose installations, while Plenum-rated cable is a required specialty item for commercial buildings with air-handling ceilings.

8. Does your factory supply both CMP and CMR rated bulk fiber optic cable?

Yes, as a direct factory supplier, we manufacture and provide wholesale access to a complete range of bulk fiber optic cable, including both CMP/OFNP for plenum spaces and CMR/OFNR for riser applications.

9. What jacket materials are used in your plenum rated fiber cables?

Our plenum rated fiber cables are constructed with high-quality, low-smoke flame-retardant materials, typically Low-Smoke Polyvinyl Chloride (LS-PVC) or Fluorinated Ethylene Propylene (FEP), to meet strict NEC safety standards.

10. Is there a performance difference between plenum and riser fiber optic cables?

There is no difference in the data transmission performance of the optical fibers inside plenum and riser cables. The distinction lies solely in the fire-safety characteristics of the outer jacket materials.

11. Can I get a factory direct price on a bulk order of CMR riser cable?

Absolutely. We are a manufacturer offering factory-direct pricing on bulk orders of CMR riser cable. Contact us for a wholesale quote to maximize your project’s budget efficiency.

12. What are the fire test standards for plenum vs riser cables?

Plenum (CMP) cables must pass the rigorous NFPA 262 (Steiner Tunnel) test, which measures flame spread and smoke density in a simulated air duct. Riser (CMR) cables must pass the UL 1666 (Riser) test, which evaluates their ability to prevent fire spread up a vertical shaft.

13. Are OEM branding options available for your plenum and riser fiber cables?

Yes, we offer comprehensive OEM services for our plenum and riser fiber cables. We can manufacture the cables with your company’s branding, specific jacket colors, and custom print streams for large-volume orders.

14. What is a “plenum space” where an OFNP cable is required?

A “plenum space” is any enclosed area that facilitates air circulation for heating, ventilation, and air conditioning (HVAC), such as the space above a drop ceiling or below a raised floor. An OFNP cable is mandatory in these areas due to the risk of smoke and fire spreading rapidly through the ventilation system.

15. For a data center installation, which is better: a CMP plenum cable or a CMR riser cable?

For a data center, the choice between a CMP plenum cable and a CMR riser cable depends on the installation path. If cables are run in under-floor or above-ceiling air-handling spaces, CMP plenum cable is mandatory. For vertical runs between floors in enclosed risers, CMR cable is typically sufficient and more economical.