Beyond UL 2196 – Important Safety Findings for Fire Rated Cable Systems
If your building contains a fire rated wiring system providing power to critical life safety applications (fire pumps, emergency lighting and smoke evacuation, etc.), the standard you need to follow us UL 2196.
The current UL 2196 standard requires that fire rated wire cable systems retain electrical continuity following a 2-hour fire exposure and subsequent hose stream test. However, there is a growing body of knowledge that there are other critical safety performance parameters that may need to be included in the UL 2196 testing protocol.
What are UL 2196 Listed Cables?
Generally speaking, there are two types of UL 2196 listed cables, based primarily on the type of insulation used.
- Mineral Insulated cables: Commonly known as MI, use an inert and inorganic material such as magnesium oxide as their insulation material.
- Polymeric cables: Use an organic polymer-based material, such as silicon rubber, as insulation.
Both types of cables can and do meet existing UL 2196 fire exposure standards. However, UL 2196 currently does not test for the presence of toxic and or flammable gas created during fire testing or for tensile strength post fire exposure.
What Do New Findings Show?
nVent PYROTENAX observed in their own labs that these two cable types exhibit different behaviors during fire testing that could have significant implications for the safety of building occupants and emergency responders while minimizing damage to buildings.
To better understand and confirm these observations, An ISO9001 Certified and a Nationally Recognized Third-Party Laboratory conducted additional testing beyond the current UL 2196 standard test protocol.
- Their testing showed that silicon rubber insulation-based UL 2196 approved cables do produce toxic smoke and gases under fire conditions that can ignite and explode with forces similar to natural gas.
- When heated, cables which use organic materials in their insulation will begin to off-gas as the temperature increases.
- Significant off gassing occurs with the silicon rubber-based insulation materials as the temperature exceeds 425°C/842°F, approximately 4.5 minutes into a typical fire.
- Loss of mass for the organic silicon rubber insulation materials range from 31% to 54%. This is what gets converted to smoke and gasses
On the other hand, Cables which use inorganic mineral insulating (MI) materials produced virtually no off gasses when heated.
The Results of Mechanical Testing
Compression testing was performed on cable samples before and after exposing the cable samples to fire conditions. The compressive strength properties of the cable systems were evaluated.
This testing compared the relative effects of fire on the cables and the cables’ ability to prevent conductors from shorting or breaking under a compressive load.
PYROTENAX System 1850 cable sample exhibited the highest pre-fire test and by far the highest post-fire test failure force of 48.3 thousand pound foot.
How Can You Learn More?
With the availability of new knowledge on the safety shortcomings of UL 2196 listed silicon rubber insulation based cables under fire conditions and the availability of other listed systems that do not produce toxic and combustible gasses under fire conditions, fire safety professionals have more facts to confidently specify the safest systems.
For life safety circuits, you have to be wired differently. Never compromise when it comes to safety.
If you would like to download the lab safety report and understand the full findings, please visit our No Smoke page today.