Disturbing experience at dive shop

[rjack321]

I have 14 mins to get up to 130ft and the 32% switch on 10/70. At an average depth of 150ish. Seems tight but doable with only an al80 of 10/70. Could the 12/55 been a second deep gas? Not sure what that achieves.
70+ mins on the 32% I might be able to do if I was really toasty and relaxed
over 100mins on the 80% would be a stretch at my consumption

 

[Wookie]

Was the 12/55 meant to replace the 10/70? Its a 1.6 at 425, which is a lil' rich for my taste but I guess not totally wild.

Then nothing all the way up to 80%?

I understood that the owner wanted to replace the 32 with the 12/55. I am a strong believer in getting off of helium as soon as possible, so I like a 32 deep deco mix, but I am OC, so I understand it's apples and not apples.

Of course, the rebreather makes the most appropriate mix anyway...

 

[wedivebc]

I understood that the owner wanted to replace the 32 with the 12/55. I am a strong believer in getting off of helium as soon as possible, so I like a 32 deep deco mix, but I am OC, so I understand it's apples and not apples.

Of course, the rebreather makes the most appropriate mix anyway...

when you're on bailout it's OC anyway right? I ran a bunch of multideco scenarios including using 30/30 instead of 32% which still gave me an extra 15min so I support the get off early concept too. In fact replacing 32% with air even shortened the dive time further by 5min but it would limit other options such as SCR mode.

 

[wedivebc]

I have 14 mins to get up to 130ft and the 32% switch on 10/70. At an average depth of 150ish. Seems tight but doable with only an al80 of 10/70. Could the 12/55 been a second deep gas? Not sure what that achieves.
70+ mins on the 32% I might be able to do if I was really toasty and relaxed
over 100mins on the 80% would be a stretch at my consumption

Yes 14 minutes to 32% would be the plan we had as well

 

[PfcAJ]

I understood that the owner wanted to replace the 32 with the 12/55. I am a strong believer in getting off of helium as soon as possible, so I like a 32 deep deco mix, but I am OC, so I understand it's apples and not apples.

Of course, the rebreather makes the most appropriate mix anyway...

Did he have a deep(er) bottom gas bailout? Tryin my best to make sense of this dude's choices but im strugglin'!

 

[wedivebc]

Did he have a deep(er) bottom gas bailout? Tryin my best to make sense of this dude's choices but im strugglin'!

try reading the dude's posts.

 

[tbone1004]

@wedivebc yeah I've got nothing. I could see changing 32% to 30/30 to make less abrupt of a switch off of helium if there was a history of inner ear DCS or anything else associated with the abrupt shift off of helium rich mixes, or maybe adding a 21/35 if your GF-Lo was low enough to require deep stops, but to go from 10/70 to 12/55 is ridiculous

 

[Wookie]

@wedivebc yeah I've got nothing. I could see changing 32% to 30/30 to make less abrupt of a switch off of helium if there was a history of inner ear DCS or anything else associated with the abrupt shift off of helium rich mixes, or maybe adding a 21/35 if your GF-Lo was low enough to require deep stops, but to go from 10/70 to 12/55 is ridiculous

I have seen a case of Lights out, or oxygen slam coming off of deep mixture, my buddy (who suffers from all kinds of weird dive related maladies I've never heard of before or since) came off of 16/50 with me on to 32% at 130 feet on a 210 foot dive. She took a good breath of the 32 to verify regulator function, and boom! Lights out for her. Her eyes were open, but no one was home. From then on she made me put 20% helium in her deep deco mix which is a horrible PITA.

I found her a rebreather, and me a new buddy. She then IPE'd coming off a 325 footer where she had to untie.

 

[wedivebc]

I have seen a case of Lights out, or oxygen slam coming off of deep mixture, my buddy (who suffers from all kinds of weird dive related maladies I've never heard of before or since) came off of 16/50 with me on to 32% at 130 feet on a 210 foot dive. She took a good breath of the 32 to verify regulator function, and boom! Lights out for her. Her eyes were open, but no one was home. From then on she made me put 20% helium in her deep deco mix which is a horrible PITA.

I found her a rebreather, and me a new buddy. She then IPE'd coming off a 325 footer where she had to untie.

I am still waiting for some science behind the inner ear DCS and what factor IBCD plays in it. I have asked Ross Hemmingway on a number of occasions to explain where the .5 atm limit that triggers a warning on multideco originated and his reply was, if you don't like the warning shut it off. There are some divers that fall outside the norm physiologically and it sounds like your friend is one of them. Does she still dive deep?

BTW I did consider that the dive shop owner might have thought a switch from 10/70 to 32% might have been too extreme or he might just have been trying to sell more helium. I will talk to him about it at some point but thought I'd drop in here in case I'm missing something.

 

[aviator8]

I have seen a case of Lights out, or oxygen slam coming off of deep mixture, my buddy (who suffers from all kinds of weird dive related maladies I've never heard of before or since) came off of 16/50 with me on to 32% at 130 feet on a 210 foot dive. She took a good breath of the 32 to verify regulator function, and boom! Lights out for her. Her eyes were open, but no one was home. From then on she made me put 20% helium in her deep deco mix which is a horrible PITA.

I found her a rebreather, and me a new buddy. She then IPE'd coming off a 325 footer where she had to untie.

What is ipe’d. Non tech here but find this thread interesting.