Deep Air

[onwardsupwards]

Interested in peoples thoughts on deep air.

On the basis that narcosis causes mental impairment at what point do individuals draw the line.
Not into an agency bashing exercise here, just wondering where the cut of point is where the individual says to him or herself "the risk of not being able to react to issues due to narcosis makes this dive iffy"

Maybe there is no cut of point because divers have been accepting narcosis as a natural part of diving. I'm sure we've all heard or read the stories of divers raving about the great zen feeling of being narced at depth. Strange to me, like saying it was great being on LSD while operating a bandsaw.

[Gooey]

Rick, are you saying it was wrong of me to operate an excavator whilst on LSD and xtc???

[PMH]

IMO every dive needs to be assessed on it's merits and then planned accordingly.

we all know what things can contribute to excessive narcosis.

using the Mt for example you could do a dive to 50m in Kilsby's then the next day a 50m dive in ela and experience different levels of being narced....for mine ela would be worse

going to the tropics is less likely to be so potent with narcosis than the colder waters.

many people who go to the solomons don't use He due to cost but air can be ok given the conditions

I remember being at pics watching some  DIR guys using He for  dive into the new section...ok they would have been clearer (by 10m of narcosis) but it isn't neccessary IMO, due to the cost

the other issue is how narcosis effects us as individuals......I have known some very good divers who get narced easily between 30/40m...again this is where knowing own levels/limitations/suseptabilities and plan the dive accordingly

the other thing to consider is buddy or team diving....55m dive 2 buddies 1 on air the other on 18/45(for eg)..... diver on mix has out of air senario goes to buddy on air...instance hit of high narcosis (Ian or anyone please correct my science if required)....not good for the acsent home....so this needs to be considered as well...I think this is called isobaric counterdiffusion

deep air can be fine...but yes you need to be switched on to yourselfand your buddies...of course He is great .....97m with an END of 30m woo hoo!!!!!!!!


ps  and great topic

[Ian T]

Few Q's : New section in Pines or Pics ? I hope you mean Pines

It's not adiabatic compression ( which is the increase in temperature due to rapid compression of a gas. Adiabatic means without any loss of heat.). I think you mean isobaric counterdiffusion, where a switch to a lighter gas to heavy gas occurs on deco ( He to EANx for example), and the body starts ongassing the heavier deco gas, instead of off gassing (counter diffusion = gas going opposite way to what it should, and isobaric = at the same pressure, ie: remaining at same depth).

good topic though. Somewhere like the Shaft, more than happy to do 40m on air, Kilsby's / tropics, up to 50m. An END of 30m is something that I'd consider important when on mix though. I'd not want to be doing 100m+ dive with END of 47 m because that's what I can handle. Because of the much greater risk of a depth this extreme, the extra conservatism is valuable.

I wouldn't recommend two divers having different bottom gases though. The differences in Deco schedules alone (without considering Narcosis/emergencies) would make this pointless.

This topic leads into the question of what gas for what depths. RN, KS and I gladly use air in Weebubbie with minimal narcosis. It's white, lots of light, and very open. The additional hassle of Helium would have been a pain in the bum there (logistically). Having said that, JD and I did some deep stuff in Pines on air, when you USED to be able to get 44m in there. Very silty, dark, and running line makes it hard (JD passed the reel to me at one point since he was so off his tree). In that situation, some He would be good. We did the dive again with about a 20% He mix from a deep mix topped up, and it really took an edge off the narcosis in the same site.

[Ian T]

RN, Apologies, released i didn't answer the original question. I think it's important to call it at any time where you feel impaired as a diver. Regardless of whether it's narcosis, uncomfortable, equipment issues, silt, etc. Once a diver starts to be compromised, it's important to do something about it.

[PMH]

Few Q's : New section in Pines or Pics ? I hope you mean Pines sorry I did mean pines

It's not adiabatic compression ( which is the increase in temperature due to rapid compression of a gas. Adiabatic means without any loss of heat.). I think you mean isobaric counterdiffusion,that is what I meant, good work Ian where a switch to a lighter gas to heavy gas occurs on deco ( He to EANx for example),to be also considered when choosing a travel gas on hypoxic dives and the body starts ongassing the heavier deco gas, instead of off gassing (counter diffusion = gas going opposite way to what it should, and isobaric = at the same pressure, ie: remaining at same depth).

good topic though. Somewhere like the Shaft, more than happy to do 40m on air, Kilsby's / tropics, up to 50m. An END of 30m is something that I'd consider important when on mix though. I'd not want to be doing 100m+ dive with END of 47 m because that's what I can handle. Because of the much greater risk of a depth this extreme, the extra conservatism is valuable.

I wouldn't recommend two divers having different bottom gases though. The differences in Deco schedules alone (without considering Narcosis/emergencies) would make this pointless.agree, good point

This topic leads into the question of what gas for what depths. RN, KS and I gladly use air in Weebubbie with minimal narcosis. It's white, lots of light, and very open. The additional hassle of Helium would have been a pain in the bum there (logistically). Having said that, JD and I did some deep stuff in Pines on air, when you USED to be able to get 44m in there. Very silty, dark, and running line makes it hard (JD passed the reel to me at one point since he was so off his tree). In that situation, some He would be good. We did the dive again with about a 20% He mix from a deep mix topped up, and it really took an edge off the narcosis in the same site.

are you saying fat blokes are more suseptable to narcosis, if so I'm in touble

it all basically comes down to sensible dive planning

[JD]

2 separate issues hear from what I read.

Rick, the problem with deep air is tolerance can vary day to day. I have been off my trolley in Little Blue (at 30 odd m?) but fine in Kilsbys at 40m. The next day in Kilsbys I may not have been though. It also depends on your reaction to Narcosis. I feel OK but have trouble with tasks like reeling (as Ian pointed out) and am happy to admit that, rather than do the macho thing and pretend everything is OK. I am OK with gas management and general dive stuff, but struggle when task loaded. Some people get paranoid, some get euphoric, but knowing your limitations and understanding you are under the influence is the main thing.
I take it dive by dive. 60m in the tropics I am fine, and would be happy to do that dive. 45m in Ela Elap and I would be taking it easy and monitoring myself carefully.

I think Helium is overused. As Ian stated, a 20% mix down the back of Pines made a noticable difference. 45% for the same dive would be overkill as far as expense vs benefit goes. As Ian stated, logistics sometimes prevent the use of mix, and someone who had dived air to depth on a regular basis would be better than someone who uses He on every deep dive.

All this coming from me who uses 10/50 for pretty much everything deeper than 30m!

JD

[Ian T]

JD,
Thats cause you only need to use 3 fish farts worth of 10/50 for a dive with the SFOD (Stainless Frame of death)

[PMH]

SFOD (Stainless Frame of death)
[/quote]

now that is gold

[JD]

now that is gold
[/quote]

More of a canary yellow actually! 

[PMH]

now that is gold

More of a canary yellow actually! 
[/quote]

JD as Ian makes jokes about your CCR remeber for him to do the diving you are qualified to do he will have to raise about $200K

[JD]

I think it's time for Ian to come out of the closet.

Ian, you want an Inspo. dont you?

JD

[onwardsupwards]

Rick, are you saying it was wrong of me to operate an excavator whilst on LSD and xtc???

No Karl, you are different.

[leaky]

Shit! what is this?

This an awesome thread gents, some really good info for norberts like moi! thanks! Especially if i'm ever allowed out to play with you big boys again!

[JD]

Do you want me to have a chat with the Mrs? I brought you back in 1 piece last time, surely I have some shread of credibility now?

Rhetorical question buys, no need for a reply....

JD