Toxicity and Safety in Communications Cable
August 22, 2003
Mr. Mike Holt
RE: How do we get the NFPA/NEC to consider another aspect of fire safety?
You are the guru on the NEC. How do we get the NFPA to consider another aspect of fire safety in communications cable products? Toxicity?
Imagine a fire drill (office building, hospital, or school) where everyone was required to wear a blindfold while exiting the building. That seems sort of ridiculous, but that may replicate part of the scenario that may occur if there is a real fire. Thick black smoke or colorless and odorless gas can have the same effect on the individual.
Gas emissions, due to the heat decomposition of some return-air plenum (CMP) communications cable materials, are dangerous, because when they come in contact with water (even minute amounts), they immediately form acid. The water source that the gases use to form these acids can be found almost anywhere-moisture in the eyes, throat and lungs of individuals with whom it comes in contact. For example: due to the heat decomposition, FEP (fluorinated ethylene propylene), may emit a colorless and odorless hydrogen fluoride gas, which becomes hydrofluoric acid in the eyes, nose and throat of the individuals exposed to the gas.
Virtually everything that burns is toxic. Some materials are more toxic than others. During a fire, the occupants should try to exit the structure immediately. However, they may be blinded and choking from either heavy smoke or acids from invisible gases.
For many years we have acknowledged the issues of reduced flame spread and low smoke generation. The cables that are located in the plenum space (usually above the ceiling) are potential concealed highways for a fire to spread. Reduced flame spread is part of the safety formula. The low smoke generation property of the cable is designed to inhibit the obscuration factor associated with thick smoke. We need to see the exit signs and the pathways to safety. Smoke also has a choking effect when inhaled. That is one more reason to limit the smoke. Both flame spread and smoke are part of the testing criteria (UL910/NFPA 262 for CMP) for communications cables for use in return-air plenum space.
Safety is too important to ignore. As the public and private sectors are besieged with higher insurance premiums and liability litigation about safety issues, we asked the "BIG" question. Does the testing process for fire safety measure the TOXICITY of the cables when overheated or burned? The answer is shockingly "NO".
Measuring toxicity output from cables used in building air systems is NOT part of the testing criteria for communications cables. This important aspect of safety is completely absent from the criteria of the current of the NEC 2002 (National Electric Code) and the proposed criteria of the upcoming NEC 2005.
During the past several decades, we have seen the effect of product “toxicity” on various industries and the victims. No one can ignore the echoing repercussions from tobacco, asbestos, and lead. The finger pointing and lawsuits continue to be prominent in the news. One common area of these products seems to be the failure to warn the buyers/users about the dangers.
Currently in the cabling marketplace, limited combustible cable is touted as the premier cable construction for fire safety. The fire testing (per NFPA 90A-National Fire Protection Association) includes maximum potential heat value of 3500 btu/lb, and maximum smoke developed index of 50 for the NFPA 255 surface burning characteristics test. The cable is UL (Underwriters Laboratories) approved and marked CMP-Limited Combustible. The testing (NFPA 90A) for smoke generation and flame spread is more stringent that the tests (UL910/NFPA 262) for CMP. At this time, FEP appears to be the only material commercially available that will pass the limited combustible test. Certainly, it would seem that more stringent fire testing is good.
In the last cycle of the National Electric Code (NEC 2002) an important development for the cabling industry took place. The need to reduce the fuel load in the return air plenums was identified and the code added a provision for the mandatory removal of "abandoned" cable. This is a big step towards safety, but it does not address the toxicity issue of the cables "in use".
Can cables emit toxic gases when heated beyond their operating threshold? Yes! Toxicity can affect your ability to escape the burning building.
In summary, what you can't see can blind you. After years of research we have determined that there is no PERFECT cable. The best solution seems to be a fully informed buyer/user. Perhaps, the NEC could be amended to include Toxicity in the testing criteria for cables in the air systems.
Further Info: Web Resources
* Hydrofluoric Acid MSDS (Material Safety
Data Sheet) by DuPont
* Toxics Use Reduction Initiative – www.turi.org.
*"Cabling: What You Don’t Know
Can Kill You" article by Stephen Saunders
Copyright © 2003 Mike Holt Enterprises,Inc.