X-Message-Number: 2030 Date: Fri, 26 Mar 93 01:38:42 CST From: Brian Wowk <> Subject: CRYONICS: Fog Problem John Hagerman: > Will there be any problems with fog? How hard will it be to see down > into the room when lowering something into it? How will condensation > be prevented on the faceplate of a worker being lowered into it? And > will it rain into the room? (Sorry if this is way too naive....) Fog is always a problem, even when trying to see patients in LN2 dewars. The problem is caused by the big inrush of warm, humid air that replaces the volume of the thick dewar lid as you remove it. In a few minutes the fog settles, the vapor stratifies, and things become pretty clear. If you're in a hurry you can also insert a warm object into the LN2 causing it to boil vigorously and quickly displace the fog with dry nitrogen. Fog problems with the Cold Room are potentially worse than with dewars. Removing the cubic-meter foam sections on top will cause an enormous inrush of room air, and fog like crazy. I suggest connecting the room gas vent to a cylinder of dry nitrogen, and putting the room under positive pressure as a cube is lifted off. That should solve the problem quite nicely. (An air compressor with a cryogenic dehumidifier could be used in lieu of the gas cylinder. As a rule, you want to always push dry gas into the room or else rime ice will buildup on everything.) Also, the room vapor circulation system will have to be shut down during during these operations. This could probably be done for a maximum of about one hour. I will be discussing this issue further in other postings. Condensation on the faceplate of cryosuits is a concern of mine also. Mike Darwin of Biopreservation is doing R&D on these suits, and he believes that keeping the helmet filled with dry oxygen will prevent the problem. Bear in mind that this must be a solvable problem, or we'll never know the personal pleasure of one day walking on moons in the outer solar system. :) Concerning cryosuits: I am now thinking that cryosuits are a convenience, not a necessity for operating my Room. Cryosuits will not be needed for work in patient storage cells for the same reasons we do not currently need scuba divers in liquid nitrogen. The only serviceable equipment will be in the central "utility cell." The utility cell, which holds the circulating fans and insulated LN2 reservoir, will itself be thermally insulated from the rest of the room. (I'll give various reasons for this in another posting.) Thus for short (one hour, approx.) time periods the utility cell can be warmed by internal space heaters so that a worker in winter clothing and an oxygen mask can replace fans, etc. Remember that patient storage cells remain covered by their cubes, and insulated from the utility cell while this work goes on. And no, it won't rain into the room. --- Brian Wowk Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=2030