"Paul B. Webster VK2BZC" wrote: >>> snip >>> > Presumably - *although* - glass pipes should not melt as they should > transmit heat instead of absorbing it. But in general, the intention to > these units is usually to provide a cold light source. This is true. However, the light sources that I worked with *could* burn wood at the focal point at the end of the light pipe. The lamps in these light sources were rated at several hundred watts. > > > Inservice training on these sources is often a bit slack. I got > *very* stroppy with a nursing sister this week who wanted to switch the > light source off during a part of a procedure where the "scope" was - > temporarily - out of use. > > She was concerned about it setting fire to the white "sponge" in which > I had wrapped it. She later said it had happened once with a green one; > I pointed out it was unlikely with a clean white one and has certainly > never happened to me in the past ten years. > > My concern was with the ever present risk on turning off the light > source that it may not start the next time. I think some explanation is needed here. The reason the lamp might not restart is that it is a xenon lamp. (You can imagine these lamps as huge neon panel lamps). They have a minimum voltage required to ionize the gas. Once the gas is ionized, the lamp will continue to operate. While the lamp is being used, the firing voltage degrades and can increase above the voltage supplied by the starting circuit. Since the lamp is on it can continue to work. Turning the lamp off and then back on will now not work because it will no no longer fire. > In the middle of a > half-finished procedure, that *really* puts a spanner in the works, even > more so than the odd charred sponge. > I am sure the patient would complain more than the sponge :-) > -- > Cheers, > Paul B.