Q: Your reply to my question about non-halogen wire and cable is interesting, and I am curious as to how you got the market information--the 1% figure. I always have difficulty coming up with that kind of information.
Regarding comparative combustion toxicities, it is a problem to compare these. There is no generally agreed-upon test protocol, and often (in fact, almost always) the carbon monoxide swamps the other gases in terms of toxic effect. I would recommend to anyone interested in this problem that he or she read "Whatever Happened to Combustion Toxicity?" by John R. Hall, Jr., of the National Fire Protection Association (Quincy, MA). The article appears in Fire Technology 32 (4), 351-371 (1996). Also, there is G. Hartzell`s "Overview of Combustion Toxicology," Toxicology 115, 7-23 (1996). Both articles lead to the idea that combustion toxicity is as much a function of how the material is burned as it is a function of what is burning. What is your information source regarding combustion toxicity, and how did they get comparative numbers?
Prof. Edward D. Weil
A: As to how I got the information, I casually walked around a trade-show floor and asked the engineers from various cable manufacturers: "How much zero-halogen cable are you selling in the U.S. market?" I know most of them from my participation in the Telecommunications Industry Association (Arlington, VA) and "Ask Donna," so they are quite used to my asking such things. Not exactly scientific, but effective.
For my reference on combustion toxicities, see: www.southwire.com/sw/techlib/ieee0008.htm.
Halogens found in insulating materials include chlorine, bromine, and fluorine. The most common halogenated insulating material is polyvinyl chloride (pvc). Plasticized pvc compounds have been used for decades for insulation and jackets for building cables.
While halogens improve certain properties?flame, chemical and oil resistance?they also have some negative effects. During combustion of halogenated insulating materials, the gases produced react with moisture to form halogen acids. These acids?for example, hydrogen chloride and hydrogen bromide?create corrosion, smoke obscuration, and toxicity.
Donna Ballast is a communications analyst at the University of Texas at Austin and a bicsi registered communications distribution designer (rcdd). Questions can be sent to her at Cabling Installation & Maintenance or at PO Drawer 7580, University of Texas, Austin, TX 78713; tel: (512) 471-0112, fax: (512) 471-8883, e-mail: email@example.com.