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Moved to the Dr Deco forum hopefully for more chance of a response.
If you want to post an intro "hi my name is..." etc, go right ahead with the intro forum. Welcome to the board
I dont know much about offgassing of helium, other than its faster than nitrogen. If this is more apt in the technical diving forum i am sure Dr Deco will move it
can anyone give me a link or more info on DCS caused by helium?
Badger,
Hi, and welcome to the ScubaBoard. You'll find a lot of info here using the search feature. As for your question above, no inert gas causes DCS. It is all a case of time versus dose loading (i.e. pressure gradient).
I had used google and it seemed there was a huge negative opinion on the use of Trimix for single 80 tank dive to about 100-130'
What I have found was an opinion that stated using the 28 O2 and 25HE was dangerous because if a rec diver did not stop at 20' the HE would cause DCS.
This was based on the premise that HE saturates in this dive profile.
I have been nitrox certified by TDI 3 years ago. I had always wanted to learn Trimix for Rec depths just because it seemed to me to add a margin of safety.
Some of the opinions against a Rec Trimix certification seemed very sharp.
several posts indicated DCS from a rapid ascent but I could not find an actual case of this in my google searches.
If anyone has a link to a study or documented case I would appreciate the link.
I am a DAN member, do you think I should give them a call? I would hate to bother them with something like this.
thank you for your time and have a good day
PS, sorry about the forum, I got the email and just followed the link it gave me.
I had used google and it seemed there was a huge negative opinion on the use of Trimix for single 80 tank dive to about 100-130'
What I have found was an opinion that stated using the 28 O2 and 25HE was dangerous because if a rec diver did not stop at 20' the HE would cause DCS.
This was based on the premise that HE saturates in this dive profile.
I have been nitrox certified by TDI 3 years ago. I had always wanted to learn Trimix for Rec depths just because it seemed to me to add a margin of safety.
Some of the opinions against a Rec Trimix certification seemed very sharp.
several posts indicated DCS from a rapid ascent but I could not find an actual case of this in my google searches.
If anyone has a link to a study or documented case I would appreciate the link.
I am a DAN member, do you think I should give them a call? I would hate to bother them with something like this.
thank you for your time and have a good day
PS, sorry about the forum, I got the email and just followed the link it gave me.
Wow! You must have run across some really ancient info! Many divers, instructors and agencies are actually recommending "normoxic to hyperoxic" trimixes in these depths- for recreational (single tank, no deco) divers. What you are looking for is given a couple of names by various agencies. Try searching for "normoxic trimix" and "triox" and you should get some better data.
I had used google and it seemed there was a huge negative opinion on the use of Trimix for single 80 tank dive to about 100-130'
What I have found was an opinion that stated using the 28 O2 and 25HE was dangerous because if a rec diver did not stop at 20' the HE would cause DCS.
This was based on the premise that HE saturates in this dive profile.
I have been nitrox certified by TDI 3 years ago. I had always wanted to learn Trimix for Rec depths just because it seemed to me to add a margin of safety.
Some of the opinions against a Rec Trimix certification seemed very sharp.
several posts indicated DCS from a rapid ascent but I could not find an actual case of this in my google searches.
If anyone has a link to a study or documented case I would appreciate the link.
I am a DAN member, do you think I should give them a call? I would hate to bother them with something like this.
thank you for your time and have a good day
PS, sorry about the forum, I got the email and just followed the link it gave me.
No problems on the forum thing, its fairly common. I know of a certain group (GUE/DIR) who suggest using 30/30 for 100-120 (with 21/35 for a little deeper), check out the DIR and the technical diving forums on here, i dont know if anything has been posted regarding this on those forums, try a search - although anything less than 3 letters wont work. I could move this thread again to either the DIR or tech forums, but i will see if Dr Deco can offer any thoughts - a good trimix course might help fill in these blanks. As for 100ft+ dives, i like to start thinking of doubles or at least redundant systems at that point and of course when it comes to stops, i like to do a few on my profile no matter what the mix - i think helium requires some more than nitrox, but this is only from what i have discussed with others on the subject.
Due to helium being an inert and therefore considered a "noble gas", it cannot cause DCS. Helium is located on the far right "up and down" row on the periodic table and because of this, it possesses full electron shells and will not readily bind with other elements regardless of what kind of bond is formed. This might be way to much information, but basically, helium cannot cause decompression sickness.
Due to helium being an inert and therefore considered a "noble gas", it cannot cause DCS. Helium is located on the far right "up and down" row on the periodic table and because of this, it possesses full electron shells and will not readily bind with other elements regardless of what kind of bond is formed. This might be way to much information, but basically, helium cannot cause decompression sickness.
If this were really true, we'd all just dive heliox and ignore decompression.
Agreed with Jeff and Charlie, from my understanding the only gas we can take a reasonable amount of at various depths (obviously oxtox being an issue) is Oxygen as we can use it (metabolise i think is the term), any other gasses are stored up in tissues and released back into the blood stream as pressure is reduced - this could be any gas, but typically nitrogen and helium are the most commonly used. Their reactivity (position on the periodic table) is pretty much a non-factor as we cant use these gases, so they are on-gassed on descent and during the dive and off-gasses on ascent, during stops and after the dive.
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Originally Posted by madisonbadger
