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.

 

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

 

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