Up In Flames: Cable Flammability Ratings

May 4, 2017 at 8:00 AM

 

Fires can’t always be prevented, but with a plan in place, fires are more easily contained and people can be kept safer. The same principle applies when choosing cables for your communication network. Some cable materials can pose real threats when ignited, especially if the fire is in an enclosed space where evacuation is not an option. For this reason, cable flammability ratings were developed. Here, we’ll take a look at what these ratings mean and how to use them to keep yourself safe and keep your communications equipment from going up in flames.

 

Most commercially available cable assemblies have an outer jacket made from polyvinyl chloride (PVC). PVC is durable and flexible, making it a great option for many applications. But for all of its benefits, PVC has some serious shortcomings. In a fire, PVC cables can act as a flame accelerant and emit dangerous, toxic gases. Fortunately, there are cable jacket materials on the market that are less-flammable and much safer. These are especially good options for installations in enclosed spaces such as ships, aircraft, submarines, trains and other vehicles.

 

General Purpose (CM, CMG, CMx)

These cables comply with UL-1582. They will burn but they partially self-extinguish. These are often used for workstation cables and patch cords, but are not for use between building floors or in air plenum spaces.

 

 

Riser-rated (CMR)

Riser-rated cables are UL-1666 compliant and are designated for use in vertical tray applications such as cable runs between floors, through cable risers or in elevator shafts. In order for a cable to be Riser-rated, it must be able to self-extinguish.

 

 

 

Plenum-rated (CMP)

Plenum-rated cables comply with NFPA-262 and UL-910. They are the only cables permitted in spaces identified as air plenums, such as raised flooring systems and air handling ducts. Cables designated as plenum-rated are able to self-extinguish and will not re-ignite.

 

 

Low-Smoke Zero-Halogen (LSZH)

 

As the name states, these cables produce low-smoke and zero halogen, plus they are self-extinguishing. Because they significantly reduce the amount of smoke and eliminate harmful halogen from being emitted, they are used in enclosed spaces where smoke and fumes can injure people and equipment. For more information on LSZH cables and where they are used, check out this blog post.

 

 

 To see exactly how each of these cables burn, watch our cable flammability test videos.

 

Specialized Cabling Systems for Military Applications

April 6, 2017 at 8:00 AM

 

When you hear the word “military” you probably think of tanks, weapons and camouflage. Military communications and cabling systems may not be the first things that come to mind, but they certainly are an important part of military operations.

 

Cables being used in combat zones face more rigorous requirements than those used in everyday civilian applications. Military voice, video and data systems are designed for rapid deployment in harsh environments with exposure to extreme temperatures, shock, vibration, dust and moisture. Cables in these systems are also exposed to heavy EMI and RFI from motors, switching power supplies and nearby microprocessors, all of which can be detrimental to network performance.

 

These extreme conditions would render a commercial communications system useless, so combat-specialized infrastructure products have been designed to meet the needs of today’s combat-ready network systems.

 

Here are some examples of products and technologies designed to meet the needs of military communications networks.

 

Fiber Optics

 

By design fiber cables are immune to EMI and RFI sometimes encountered in the combat theatre. Additionally, fiber optic cables are now offered in special crush and impact-resistant designs and some military-styles are available with armored jacketed cable.

 

Connectors such as the Straight Tip (ST) are fitted with heavy tension springs to ensure proper mating when exposed to major shock and vibration. They are also offered with locking mechanisms for additional protection against optical disconnects.

 

Other fiber optic connectors for military applications feature Ingress Protection (IP) rated designs with screw lock mating and extra-strength strain reliefs of over 250 Newton’s to ensure a solid connection during field use.

 

Shielded Ethernet Cable

 

Shielded Cat5e or Cat6 copper cables are the way to go when fiber cabling isn’t an option. Military applications require shielded twisted pair (STP) copper cables and rugged military-style connectors for most applications. STP cabling reduces the damaging effects of EMI and RFI sometime encountered in the field.

 

Other Ethernet cabling options for military apps include IP68 rated cables that utilize ruggedized Anodized or Zinc Alloy finished connectors and double shielded, high-flex, UV and Oil resistant FR-TPE (Flame Retardant Thermoplastic Elastomer) jacket that is CMX outdoor rated to stand up to the toughest environments.

 

Jacket Compounds

 

Whether you’re using fiber or copper cables, the cable jacket compound should always be taken into consideration. The outer cable jacket of many copper and fiber cables is usually made of PVC material that is toxic when burned and can accelerate a fire spreading.

 

Low-smoke zero-halogen (LSZH) jackets are a much safer solution and a popular choice for military applications. As the name implies, LSZH cables produce minimal smoke and no halogen, both of which can be harmful to people and expensive communications equipment. LSZH cables will also self-extinguish which makes them ideal for enclosed spaces such as ships, aircraft, tanks and other vehicles.

 

Polyurethane jackets are sometimes used in military applications because of their ability to withstand damaging UV rays, oil and petroleum-based products, and mechanical abuse. Though cables with a Polyurethane jacket will also release toxic gases and will not self-extinguish like LSZH cables.

 

The Benefits of LSZH Cables and Where They are Used

January 26, 2017 at 8:00 AM

 

Since the discovery of fire, humans have been taking steps to protect themselves from fire’s harmful effects. Cables in communication applications are not exempt from catching fire and can produce harmful smoke and gas, so preventative measures have been taken to make sure that cables are safe too – hence, the development of LSZH cables.

 

Low-Smoke Zero-Halogen (LSZH) refers to the material in the cable’s outer jacket. Most commercially available cable assemblies have an outer jacket made from polyvinyl chloride (PVC). PVC is a durable, flexible plastic that is perfect for most applications, but one of the biggest downfalls of PVC is the way it burns. Once PVC has caught fire, it typically burns freely for a long time and releases toxic gas in the process.  On the other hand, LSZH cable jacketing is made of thermoplastic or thermoset compounds that emit limited smoke, no halogen and won’t produce dangerous gas when exposed to high sources of heat.

 

In a building fire, there is a danger of standard PVC cables burning behind the walls or in ceilings for a long period of time and that fire spreading from room to room or floor to floor and creating toxic gasses. Though in most building fires, occupants are able to evacuate and escape these gasses, but sometimes getting out of the building isn’t an option.

 

LSZH cable jackets are becoming increasingly popular in applications where people are in close proximity to cable assemblies and cannot easily get ventilation in the event of a fire, such as military, aerospace, railroad and maritime applications. Cost effective LSZH jackets are typically used, and sometimes required, in poorly ventilated areas such as onboard aircraft, military vehicles, submarines and ships. They are also used extensively in railway systems, wherever high voltage or track signal wires are run through underground tunnels. This reduces the chance of toxic gasses accumulating in these areas if the cables caught on fire.

 

In the event of a fire, an LSZH cable jacket can be instrumental in protecting people from fire, smoke and dangerous gas emitted from the burning cables. L-com offers a wide-range of LSZH cable assemblies thatare designed for use in areas where toxic smoke could damage sensitive equipment and enclosed areas where air quality is a concern.  For more information, check out our LSZH cable assembly product guide.

 

Hot Stuff! Low Smoke Zero Halogen (LSZH) USB Cables

December 3, 2013 at 10:00 AM


Flammability and Toxicity Ratings on Different Cable Types

 

 LSZH USB CableLSZH USB Cable

 

 

What would happen if your cables caught on fire?

 

There's actually much more to consider than the obvious flames and danger. Gasses you can't see and destruction to the inner cable conductors can endanger lives and destroy valuable communications equipment. 

 

To avoid that unknown, here’s a snapshot of USB cable jackets and looking into what yours is made of. Most commercially available cable assemblies have an outer jacket made from polyvinyl chloride, or PVC for short. Another alternative chemical compound that a cable's outer jacket can be made of is called Low Smoke Zero Halogen (LSZH), which reduces the amount of toxic and corrosive gases emitted during combustion.   

 

PVC is a durable, flexible plastic material perfect for most general applications.  If you were to buy a deluxe or premium USB cable, PVC is the type of jacket it would have. Yet for all of its benefits, PVC has some downsides- the biggest of which is the way it burns

 

Once PVC has caught fire it typically burns freely for a long while and releases toxic gasses in the process, including harmful halogens. In a building fire, the danger is that flames can burn along the cable jackets behind a wall and leap from room to room or floor to floor.   In most building fires the toxic gasses are not a big factor since occupants can get outside, and since USB cable is rarely run behind a wall, most manufacturers don't bother making them with non-PVC jackets.

 

But in some instances, a building fire isn’t the only scenario to consider.  Military and aerospace applications add another element to the danger:  people don’t always have outdoor access.  In fact, any application where people are working in close proximity with cable assemblies and cannot easily get ventilation in the event of a fire would require a special jacket material for the cables.

 

USB with LSZH Jackets

 

Though USB is not often run behind a wall and the USB standard is typically only used in peripheral-to-computer applications (including many in military and aerospace environments), having many PVC USB cables can lead to a dangerous situation.  LSZH cables, on the other hand, are self extinguishing. For that reason, L-com has made LSZH USB cables an off-the-shelf product, available for same-day shipping. 

  

 

Standard LSZH USB cables are constructed similarly to the premium line of USB cables: they have 20 AWG power conductors for maximum power transfer, and have 30 micro inches of gold on the contacts to ensure reliable connections through multiple mating cycles. Along with the standard type LSZH cables, L-com also carries a line of its "latching" USB cables with LSZH jackets.  These cables have small latches in the Type A connectors that lock the connector in place.

 

LSZH USB cables with Latches prove to be especially valuable in high-vibration environments such as in a military vehicle or in a device that is meant to be carried over rough terrain. Don’t overlook endangering personnel and valuable communications equipment by using standard PVC USB cables; LSZH USB cables might be better for your application.

 

For more information check out our ratings chart below, or this helpful video on cable flammability tests.

 

USB Flammability Ratings

 

Choose the Right Cable Jacket Material

July 17, 2013 at 10:00 AM


Plenum, LSZH and More

 

L-com's Plenum rated multiconductor cable

 

For buyers and technicians using signal-grade cabling, much attention is usually given to the connector type, termination process and bulk cable construction. Another aspect not to be forgotten that can be critical to many applications is the cable jacket material.

 

 

What does the jacket do?

 

More than just a color coding cable management technique, the jacket has several important functions. It allows the separate conductors to be organized into a single data line for ease of organizing, or it can even contain several conductors or wires to be broken out at a drop point.

 

The cable jacket also aids tremendously in the cable's flexibility and durability. In covering any shielding within the cable, it can prevent noise that collects on the shield from degrading the signals of other cables nearby, or from draining at inappropriate spots. Finally, the outer jacket is often the last line of defense between the data-carrying conductors and the environment in which the cable is used.

 

 

Fire Code Considerations

 

Comparison of cable jackets burning

Perhaps the most important aspect of a cable's jacket is how that jacket burns in a fire. PVC, the flexible plastic material that makes up most general purpose or residential grade cables is cheap and convenient, but it burns quickly and releases poisonous gas while burning.

 

If cables are run behind the walls of a building or in a vehicle and a fire breaks out, that fire can "leap" from room to room or floor to floor by burning along the cables behind the walls. And if the location where the cables are run is difficult to exit, as in a submarine, ship, airplane or even crowded warehouse, the poisonous smoke would compound the difficulty in dealing with the fire.

 

Because of this, many cables are given flammability compliance codes to help technicians from buying or using inappropriate cables. But, differences in measurement techniques and designations can make the process very confusing. In general, though, there are two "types" or classes of jacket materials other than PVC.

 

 

Plenum for Fire Retardation and Self-Extinguishing

 

In many large buildings, the duct work between rooms and floors is also the raceway for much of the building's data cabling. This space is often called the building's "plenum", and so the types of cables run in these environments are often called Plenum rated cables or just Plenum cables.

 

Plenum materials must be self-extinguishing, meaning that after they start burning and then the external fire or heat source is removed, the material must stop burning. This prevents the cables from "carrying" the fire to another location in the building and re-igniting unexpectedly. Sometimes Plenum cables are referred to as CL2P, OFNP, or CMP. Plenum cables are known to be more expensive than PVC, but in cases where a fire code requires plenum the cost must be factored into the overall installation job.

 

 

Low Smoke, Zero Halogen (LSZH) for Sealed or Mobile Locations

 

Jacket materials that have been designed to release very little smoke and no poisonous gas when burned are often called LSZH. These are typically reserved for special applications where the occupants near the cables may not be able to escape or ventilate the room in the instance of a fire. Again, this occurs frequently in military and aerospace applications.

 

 

Special Jacket Considerations

 

In addition to the above designations for particular fire codes, jackets may have other features useful in niche applications. UV resistance is important in applications where the cable may be exposed to strong sunlight for long periods. UV light can weaken and eventually destroy many PVC compounds over time. Or, oil resistance may be needed in many factory automation apllications as the petroleum-based compound could dissolve if immersed in oil. High-flex or hi-flex cables often use a special jacket that will not crack and split when the cables are flexed over and over again.

 

If you're looking for industry's largest selection of off-the-shelf Plenum, LSZH and other special-jacketed cable and cable assemblies, stop in at L-com's online configurator or contact customer service to get a quote started. We can custom manufacture cables with the jacket type you need.

 
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