George, I once worked in a laboratory that developed the Doppler weather radar we all see on TV today. In our just built (in 1979) control room, they put a halogen extinguisher system. Halogen works by displacing the oxygen and thus the fuel for the fire. No fuel, no fire. The system could fill the entire control room, 50' x 80' in less than 30 seconds. We had big klaxon alarms and a disable mechanism, but strict rules to just run like hell. We had a 10 second warning bell that went off just before the gas came down. Point is, it wasn't so much the ozone layer that made halogen fall out of favor, it was the severe threat to human life. The gas is odorless, tasteless and invisible, so if it went off you wouldn't know until too late. I recall they told us that you would not live 30 seconds in a room filled with halogen. The several false alarms caused us to evacuate and we had to call the fire department to ventilate the building for 60 minutes before we could get back to work. Halogen is certainly an extremely effective means of suppressing fire, but operating costs and impact on operations play a big part in its use (or lack thereof). The gas is expensive and, while there is little damage to facilities or equipment from its use, there can be human consequences to deal with.
Scott [email protected] ECRM Incorporated Tewksbury, MA USA -----Original Message----- From: [email protected] [mailto:[email protected]] Sent: Wednesday, November 17, 1999 9:42 AM To: [email protected] Subject: RE: Shielded Enclosure Fire Hazard Importance: Low Between a hard place and a rock........ It is hard to argue that EMC chambers should not have fire protection. The newer tiled facilities may have little combustible content other than the DUT. However, most factory insurance carriers will insist on an adequate prevention and extinguishing system. However........ If a water system is used, and goes off due to a fire OR a perceived fire, the water tends to ruin the typical cones. Result, big expense! Our oldest chamber has a halogen system, with a staged set of alarms. The alarms provide the opportunity to reset if someone merely plugged a 120V device into the 230V mains and produced some smoke, or any other false alarm. The halogen, if deployed, does no damage to the facility. Now the tricky part. Halogen has a bad rap due to the shrinking ozone layer and all. It may be difficult? to install halogen on new systems. The bad news is that such systems require a fair amount of stored halogen. The good news is that under proper installation, staged alarms, and good use of the chamber, the system should NEVER have to dump the halogen. If a real fire occurs, the halogen is the most efficient extinguisher, and can save a good deal of $$. But then there is that ozone layer............. Of course, regardless of the gas or fluid used in such systems, the sensors, piping, and nozzles must generally be as non-conductive as possible to preserve the needed chamber EMC characteristics. George Alspaugh Lexmark International Inc. --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
