hale@ucsd.edu> (05/24/91)
In article <telecom11.382.1@eecs.nwu.edu> leichter@lrw.com (Jerry Leichter) writes: [ good discussion about Halon deleted ] > I watched a test of a Halon fire supression system installed at Yale a > number of years ago. The testers remained inside the room as the > system was set off; they seemed quite unconcerned. A decent-sized > Halon system is pretty impressive to watch when fired: It has to get a > sufficient concentration of Halon throughout a room FAST. This > requires that the Halon be forced into the room at high pressure, > creating quite a wind -- all sorts of things go flying. Also, as the > Halon expands rapidly, it undergoes adiabadic cooling, rapidly > dropping the temperature in the room -- so the room instantly fills > with fog. In all, a startling experience if you aren't prepared for > it -- but not in and of itself dangerous. I suspect that the test you witnessed was performed with a dummy substance in the tank rather than Halon. The cost of a tank of Halon suitable for a typical computer room is several thousand dollars for the Halon alone. When my employer had the Halon system tested here they used a dummy material that fogged up the room for a few minutes. The mist is apparently used to decide where the gas flows and how well it covers the intended area. I was an unwitting participant in a real Halon discharge. Two schmucks from a private fire company had been fooling with the fire alarm system all morning and hadn't succeeded in what they were trying to do. I and several others were standing in a newly constructed area, soon to be equipped with a raised floor. Suddenly a noise comparable to a jet aircraft passing overhead at 50 feet altitude started and continued. My first thought was "that jet must be in serious trouble and will probably crash across the street." When the sound didn't change after a couple of seconds my next thought was "it's not a plane, it must be a break in one of the high-pressure gas lines we have here. What kinds of gases do we have in the building? Compressed air - no problem. Dry nitrogen - probably OK, we'll just have to get out of this room soon. Hydrogen - get the **** out of here instantly!!" But then I realized that if it were hydrogen it would explode before I could move more than a couple of paces so I just stayed put. Soon the sound stopped. There was no mist or other visual effect (aside from the trash on the floor being blown all over the room). We remained in the room for a few minutes and then went to the adjacent area which was also physically unaffected. About fifteen minutes later the fire company employees arrived to find out if the Halon had been discharged. The situation was very close to a lynching at that point. This was a fairly small area and the Halon tank only cost about $1800 to refill. None of us suffered any adverse physical effects from it. Bob Hale ...!ucsd!btree!hale 619-535-3234 ...!btree!hale@ucsd.edu
Macy Hallock <macy@fmsys.uucp> (05/26/91)
[ good discussion about Halon deleted ] >> I watched a test of a Halon fire supression system installed at Yale a >> number of years ago. The testers remained inside the room as the >> system was set off; they seemed quite unconcerned. > I suspect that the test you witnessed was performed with a dummy > substance in the tank rather than Halon. This is true. In a decent size computer room, a Halon 1301 dump can cost $10k-30k. For this reason, testing is done using another gas. The tests I particpated in (one of the companies I own does fire alarm work, and I hold a valid State of Ohio Fire Alarm Installer License) used CO2. I was told CO2 dispersed in a similar fashion as Halon and cost far, far less. All personnel were evacuated prior to the test. The only people remaining in the room had breathing gear on. (It looked like fire/mine type assisted breathing apparatus to me) The discharge itself was rather spectacular, and sure stirred up the air. A slight mist/fog could be seen. The air temperature dropped several degrees, according the the evironmental systems. Frost formed on the manifold and pipes above the tanks, and on the halon tanks themselves. The sound was impressive, too. I'm told the actual change in the air mixture in the room is rather rapid and when either halon or CO2 is used, should not be deadly. However, the possiblility of accidental asphyxiation is possbile, either by incomplete dispersal (the high discharge veolcity is intended to even mix/disperse the gas) or for physical reasons (poor health, etc>). Accordingly, the correct procedure is to evacuate without delay, and reenter only with assisted breathing apparatus until the room's atmosphere is returned to normal. Later, after I was off site, some idiot got to fooling around with the room's fire alarm system and dumped the real halon. The bill was around $20k at this site (a major insurance company), and the idiot tried to blame our fire alarm system. We had to demonstrate the system operated well within spec and also got written statements from several other people in the computer to resolve the issue. Sigh. I really didn't want to learn about Halon systems to the extent required by the situation. Note that the computer room involved was actually smaller than most major central office ESS equipment rooms are. I now notice that some of the local telcos and carriers are installing Halon systems. They are also breaking up their offices into smaller areas and using firestops and doors to compartmentalize their Halon systems and fire risks. Its about time. Macy M. Hallock, Jr. N8OBG 216-725-4764 Home macy@fmsystm.UUCP macy@NCoast.ORG Note: macy@ncoast.org is best reply path to me. uunet!aablue!fmsystm!macy [No disclaimer, but I have no real idea what I'm saying or why I'm telling you]