Letters

In response to the letter written by Dean K. Wilson (CSE 03/02 p. 9), regarding his article "Circuit Integrity Cable Re-Examined" (CSE 09/01 p. 55), as pointed out in his letter, indeed, circuit integrity fire-alarm cable was not shown in the Pyrotenax video, and we agree that the effect is less pronounced in this type of cable, simply because of the amount of insulation involved.

However, the gases produced by decomposition of types MC and RHH cable under fire conditions should not be compared with those from conventional cables. One difference between these cables and other polymeric cables is the application in which they are used. These cables are intended specifically for critical life-safety circuits in buildings for equipment such as fire pumps and emergency generators.

The flammable gases they introduce during a fire are capable of being funneled directly into the emergency equipment enclosure, where an arcing contact could cause ignition. There are other differences, but on this basis alone—that emergency circuit wiring might introduce a hazard threatening the emergency power supply—there is a safety issue that needs to be addressed. Conventional cables are not used for fire-rated circuits, except as part of an electrical circuit protective system. There are 25 electrical circuit protective systems listed in the 2002 Fire Resistance Directory.

In should be noted that only the systems using ceramifiable insulation introduce the hazard in question. But any chance of a hazard occurring is too much of a chance to take when lives are at stake.

Barry O'Connell, P.Eng., Commercial Marketing Manager Tyco Thermal Controls (Formerly Pyrotenax Cable Ltd.)

Correction: In the news story "Halon Replacements Still a Hot Topic," (CSE 06/02 p. 16) the item incorrectly noted that the U.S. would be under mandate to replace Halon by 2003. The article should have reported that Europe was under mandate to do so. We apologize for the error.