Many industrial Ethernet cables are designed to limit flame spread, but flame performance depends on the jacket material and certified fire rating. Understanding CM, CMR, CMP, LSZH and standards such as UL 1581 and IEC 60332 helps engineers select cabling that meets the safety, installation and compliance requirements of industrial environments.
Key Takeaways
- Not every industrial Ethernet cable is flame-retardant; always verify the cable jacket, fire rating and applicable test standard on the specification sheet.
- Flame-retardant and fire-resistant are not interchangeable: flame-retardant cable limits flame spread, while fire-resistant cable is designed to maintain operation during fire exposure.
- CM, CMR and CMP indicate different fire-performance levels and installation environments, with CMP intended for plenum air-handling spaces.
- LSZH cable is designed to produce less smoke and fewer halogen gases when burned, making it valuable in enclosed or evacuation-sensitive environments.
- Industrial installations should match cable ratings to local code requirements and standards such as UL 1581, UL 1666, UL 910 or IEC 60332.
In industries where heavy machinery, high electrical loads and combustible substances are the norm, fire safety is essential. Industrial Ethernet cables, the backbone of modern automation networks, must often endure extreme heat, mechanical stress and potential fire hazards. But are they flame-retardant?
Some industrial Ethernet cables are engineered to be flame-retardant, but not all of them are, and the degree of flame resistance varies depending on materials, construction and certification.
What Does Flame-Retardant Mean for Ethernet Cables?
A flame-retardant cable is designed to limit ignition and flame propagation under specified test conditions. In a fire event, a fire retardant Ethernet cable is intended to slow burning and self-extinguish once the flame source is removed, as defined by the test it was evaluated against.
Flame retardancy describes flame behavior only. Smoke production, halogen content and the ability to keep operating during a fire are separate performance characteristics, and a cable’s datasheet should declare each one individually. Industrial Ethernet cable is not automatically low-smoke or fire-resistant just because it is flame-retardant.
Why Flame Retardancy Matters in Industrial Environments
Industrial environments such as factories, oil and gas facilities, refineries and food processing plants contain ignition sources, chemicals, machinery and extensive wiring. Long cable runs and cable trays packed with bundled cables can give a fire a path to travel. A fire that spreads along trays or bundles can cripple operations and put lives at risk.
A cable that does not limit flame spread can contribute to fire moving along trays and conduits, endangering workers and damaging equipment. A flame-retardant cable is engineered to resist ignition and limit fire spread, which helps protect personnel and reduces the risk of costly downtime on mission-critical industrial networks.
Fire-rating requirements are not identical for every installation. They depend on local building codes, the type of facility, insurer requirements and where the cable is installed, so the required industrial Ethernet cable fire rating should be confirmed for each project.
Flame-Retardant vs. Fire-Resistant vs. LSZH Cable
These terms are easy to confuse, but they describe different characteristics:
- Flame-retardant cable limits flame propagation.
- Fire-resistant cable is designed to maintain circuit integrity for a specified period under defined fire conditions.
- LSZH cable is evaluated for smoke and halogen-related performance, meaning it is designed to produce less smoke and fewer halogen gases when burned. This makes an LSZH Ethernet cable useful in enclosed spaces.
Industrial Ethernet cables may be flame-retardant by design, but they are not necessarily fire-resistant unless built for specialized applications. A fire resistant Ethernet cable is typically evaluated against circuit-integrity standards such as EN 50200, which tests whether a cable can remain operational for a specified time during fire exposure. For example, cables such as the ETHERLINE® FIRE series are designed to maintain insulation integrity for 120 minutes during a fire, making them suitable for safety-critical zones where continuous operation is essential.
US Cable Ratings: CM, CMR and CMP
In the United States, communications-cable fire ratings are primarily defined through the National Electrical Code (NEC, also known as NFPA 70) and Underwriters Laboratories (UL). The NEC specifies fire safety requirements for electrical installations, including guidance on plenum and riser applications. UL test methods are then used to evaluate how cables perform under flame conditions:
- UL 1581 is a reference standard for wire and cable test methods. It includes the VW-1 Vertical Wire Flame Test, which simulates a cable burning in a vertical position to assess whether the flames self-extinguish. Passing this test shows a cable’s ability to limit upward flame spread. This is the basis of the UL 1581 flame test.
- UL 1685 is the Vertical Tray Flame Test. It evaluates flame spread in bundled cables mounted in trays, which closely mirrors conditions in many industrial environments where cable trays organize and support large numbers of cables.
Three principal classifications are used for communications cables:
- CM is a general-purpose communications-cable classification and the most widely used.
- CMR (riser-rated) is intended for qualifying riser installations, such as vertical shafts running between floors. It is tested under UL 1666, which is more demanding than the general-purpose CM classification.
- CMP (plenum-rated) is intended for qualifying plenum and other air-handling spaces and represents the highest of the three levels. It is tested under UL 910, which measures both flame spread and smoke production. A plenum rated Ethernet cable commonly uses low-smoke jacket compounds such as fluoropolymers.
If a cable does not carry a CM, CMR or CMP rating, or an international equivalent, it may not meet the requirements for the space where it is installed.
Installation location determines the required communications-cable classification, so review this broader guide to cable flammability ratings before selecting CM, CMR or CMP cable.
IEC 60332 Flame-Propagation Tests
Globally, IEC 60332 is one of the most widely referenced sets of flame-propagation tests. It is divided into parts that address different conditions:
- IEC 60332-1 covers testing on a single vertical wire or cable, evaluating flame resistance on an individual cable.
- IEC 60332-3 is a series covering vertically installed bunched cables under defined test conditions. It measures flame spread when multiple cables are bundled together, which better reflects real-world installations.
IEC 60332 is not a single universal cable certification. A cable may be tested to one part and not another, so an IEC 60332 cable should be specified by the exact part and category it meets. In the European Union, the Construction Products Regulation (CPR) also classifies cables from Aca (non-flammable) to Fca (highly flammable), with classes such as B2ca and Cca indicating different levels of fire performance for building installations.
How Jacket Materials Affect Smoke and Flame Performance
The choice of jacket material plays a major role in a cable’s fire behavior. Material selection affects flame spread, smoke, corrosive gases, flexibility and environmental resistance:
- PVC (polyvinyl chloride) is the most common option. It offers flame-retardant properties by melting or charring instead of flaring rapidly, but PVC cables can emit smoke and halogen-containing gases when burned.
- LSZH (low smoke zero halogen), also known as LSOH, is designed to produce minimal smoke and no halogen gases when burned. This makes LSZH Ethernet cable a common choice for tunnels, transportation systems and data centers. Its flame performance still depends on the specific compound and the tests it has passed.
- PUR (polyurethane) is frequently used in flexible or robotic cables and can be formulated to include flame-retardant properties.
- Fluoropolymers such as FEP and PTFE are used in plenum-rated cables. They offer high temperature stability and low smoke, but they contain fluorine, which is a halogen, so they should not be described as halogen-free.
Pro tip: For tunnels, trains, offshore installations and public buildings, look for LSZH or LSOH together with a stated flame-test standard. Where circuit integrity matters, also look for a declared fire-resistance rating.
Fire performance is only one part of jacket selection, so compare PVC, PUR and TPE cable jacket materials for differences in flexibility, abrasion resistance and environmental suitability.
How to Verify an Industrial Ethernet Cable’s Fire Rating
Use this checklist to confirm that a fire retardant Ethernet cable meets your project requirements:
- Check the cable jacket marking and technical datasheet. Look for CM, CMR or CMP (or an international equivalent such as IEC, EN or CPR), and for explicit references to flame retardancy, LSZH or fire behavior.
- Confirm the exact listing or test standard. For example, UL 1581, UL 1666, UL 910, IEC 60332-1, IEC 60332-3 or EN 50200. An IEC 60332 cable should name the specific part.
- Match the rating to the installation location. Plenum spaces, riser shafts, cable trays and general-purpose runs can have different requirements. A plenum rated Ethernet cable is intended for qualifying plenum spaces.
- Check whether smoke, halogen and circuit-integrity performance are separately declared. Flame retardancy does not guarantee low smoke, low halogen content or continued operation during a fire.
- Confirm applicable requirements with the project engineer or authority having jurisdiction.
Building pathways also affect cable selection, so review how backbone, horizontal and patch cabling fit within LAN and premise architecture.
Are All Industrial Ethernet Cables Flame-Retardant?
No. Flame performance depends on the specific product’s construction, markings, certification and intended installation. Some industrial Ethernet cables are flame-retardant, and the level of performance varies from one cable to the next.
If a cable lacks fire-rating markings or declared test standards, do not assume it is flame-retardant. Confirm its fire performance before using it in any industrial, public or safety-affected environment.
For industrial environments, whether a steel mill, refinery, data center or smart factory, a certified fire retardant Ethernet cable that is matched to the installation helps limit fire spread and supports compliance with applicable requirements. For mass-occupied, transport or escape-route settings, also consider LSZH cable.
Frequently Asked Questions
Are All Ethernet Cables Flame-Retardant?
No. Flame performance depends on the specific cable’s jacket, construction and certification. Confirm the fire retardant Ethernet cable rating on the cable marking and datasheet.
Do I Need Flame-Retardant Cable Outdoors?
Outdoor suitability and flame rating are separate characteristics. The required rating depends on the complete cable route, including whether the cable enters a building or passes through a regulated space. Where a fire retardant Ethernet cable is required, check both its fire and environmental ratings.
What Happens if the Cable Does Not Have the Required Rating?
Using an incorrectly rated cable may create a safety or compliance issue. Requirements vary by jurisdiction and installation, so confirm them before installing a fire resistant Ethernet cable or plenum rated Ethernet cable.
What Is the Difference Between Flame-Retardant and Fire-Resistant Ethernet Cable?
Flame-retardant cable is designed to limit flame propagation. Fire-resistant cable is designed to maintain circuit integrity for a specified period under defined fire conditions.
What Do CM, CMR and CMP Cable Ratings Mean?
CM is a general-purpose communications-cable classification. CMR is intended for qualifying riser installations, and CMP for qualifying plenum and air-handling spaces.
Is LSZH Ethernet Cable Flame-Retardant?
Not automatically. LSZH describes low smoke and low halogen performance, which is evaluated separately from flame propagation. Check the datasheet for the flame-test standard the cable has passed.
Which Flame Tests Apply to Industrial Ethernet Cables?
Common tests include UL 1581 (including VW-1), UL 1685, UL 1666 and UL 910 in North America, and IEC 60332-1 and IEC 60332-3 internationally. The applicable test depends on the cable type and installation.