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--=====================_6645621==_.ALT Content-Type: text/plain; charset="us-ascii"; format=flowed At 11:22 AM 3/14/00 +0200, Simon Murray wrote: >I had a conversation with a long term hardened stroke over the weekend and >he told me that his non-crushed neoprene dry suit does not change its >buoyancy characteristics as he goes deeper because the helium that he uses >to inflate it penetrates the neoprene and stops it from crushing. > >Sounds like one of the best stroke stories I have ever heard, or am I >completely missing something ? Apart from the insanity of using helium as an insulator there's some truth to this -- helium does seep into neoprene. Sat divers want to keep their suits and gloves in water rather than in a helium atmosphere. Otherwise the neoprene swells during decompression. A humongous helium-blown glove provides little insulation. Helium is a terrific heat conductor. As an aside there are current posts on the difference between heat conductance and heat capacity. In plain English, helium is a very poor insulator (inflation gas) but it's not colder to breathe a gas containing helium. Any gas you inhale will be heated to body temperature before you exhale it. The question is "what does it cost to heat it?" rather than "how well does it conduct heat?" Answer: less than air / nitrox. However, since helium heats instantly in your mouth you feel it. Nitrogen may not heat before it's in your lungs. You are less sensitive to heat loss from your core, thus you don't feel the heat loss. Get the picture? regards, Hans --=====================_6645621==_.ALT Content-Type: text/html; charset="us-ascii" <html> At 11:22 AM 3/14/00 +0200, Simon Murray wrote:<br> <font face="Times New Roman, Times"><blockquote type=cite cite>I had a conversation with a long term hardened stroke over the weekend and he told me that his non-crushed neoprene dry suit does not change its buoyancy characteristics as he goes deeper because the helium that he uses to inflate it penetrates the neoprene and stops it from crushing.</font><br> <br> <font face="Times New Roman, Times">Sounds like one of the best stroke stories I have ever heard, or am I completely missing something ?</font></blockquote><br> Apart from the insanity of using helium as an insulator there's some truth to this -- helium does seep into neoprene. Sat divers want to keep their suits and gloves in water rather than in a helium atmosphere. Otherwise the neoprene swells during decompression. A humongous helium-blown glove provides little insulation. Helium is a terrific heat conductor.<br> <br> As an aside there are current posts on the difference between heat conductance and heat capacity. In plain English, helium is a very poor insulator (inflation gas) but it's not colder to breathe a gas containing helium. Any gas you inhale will be heated to body temperature before you exhale it. The question is "what does it cost to heat it?" rather than "how well does it conduct heat?" Answer: less than air / nitrox. However, since helium heats instantly in your mouth you feel it. Nitrogen may not heat before it's in your lungs. You are less sensitive to heat loss from your core, thus you don't feel the heat loss. Get the picture?<br> <br> regards,<br> <br> Hans<br> </html> --=====================_6645621==_.ALT-- -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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