Which do you think is less dangerous at 160ft? Open-circuit air or CCR trimix?

[rongoodman]

Let me just briefly quote some famous and highly respected divers on deep air dives.
1947 Frederi Dumas 308 ft
1961 Hal Watts 350 ft
1965 Tom Mount 360 ft
1971 Sheck Exley 466 ft
1993 Bret Gillian 475 ft

Perhaps there's a reason that the last of these dives was carried out over 30 years ago.

 

[PfcAJ]

Yes, yes, I have heard all this, many times before. I can also quote may divers who have lost their lives on rebreathers. The ratio of rebreather deaths to open circuit scuba deaths has been quoted as about 5 to10 rebreather deaths to every single open circuit scuba death.

Certainly, I have dived with some individuals who have experienced narcosis at 100 feet. In fact, I rescued a buddy diver who was narked out (asleep on the bottom with his eyes open) at the end of a 25 mins deco dive at 140 feet on air.

Consequently, for some people narcosis is a serious problem. However, some individuals can function despite narcosis at considerable depth.

Whether you use a rebreather or open circuit scuba, it is a question of analysis of dive site conditions, individual susceptibility/capability with narcosis, individual perception of risk, good risk assessment to identify and mitigate problems and proper dive planning.

Also, trimix is not easily available all over the world. In some cool remote locations, all you can find is air. Therefore, if you have a rebreather you may have to use air as a diluent.

In conclusion, whether you use a rebreather on trimix or open circuit on air to 160 feet, both approaches present risks. It is your individual choice based on sound risk assessment. To quote Sheck Exley "what works, works".

Let me just briefly quote some famous and highly respected divers on deep air dives.
1947 Frederi Dumas 308 ft
1961 Hal Watts 350 ft
1965 Tom Mount 360 ft
1971 Sheck Exley 466 ft
1993 Bret Gillian 475 ft

Sheck died breaking his own rules.

Great example.

 

[CG43]

Perhaps there's a reason that the last of these dives was carried out over 30 years ago.

The list goes on :

1999 Scarlett Watts women world record deep air 129 m (425 feet) .
1999 Mark Andrews men's world record deep air 158 m (519 feet)

But what impressed me the most is that Hal Watts dived with 55 divers to depths between 100 m (300') and 127 m (415') without one accident .
Hal Watts

 

[Nick_Radov]

For any dive up to 200 feet on air I am comfortable with open circuit. For me narcosis is just a single risk and it is workable.

Rebreathers on trimix remove the risk of narcosis but introduce a whole swag of other risks. Hyperoxia, hypoxia, hypercapnia, flooding, sodalime inhalation, etc.

Hypercapnia is just as much a risk on open circuit deep air due to the relatively high WOB and gas exchange issues.

In Cousteau’s day, the above simply weren't available to the pioneers. It is available and trained these days. A bit of narcosis is OK, but being off your face with narcosis at 50m/165ft isn't fun and you're absolutely relying on your experience to get through the dive. Personal memories of having an in-depth conversation with lobsters and blennies... I choose trimix and a rebreather so I can enjoy the dive and rummage around in the sunken museum, whilst doing a long dive and reliable deco so I can do the same for the rest of the week.

Even Jacques-Yves Cousteau himself had switched from air to trimix starting in 1976 for the really deep dives.

1975-6 Cousteau

THE TEAM Expedition Leader (France): Jacques-Yves Cousteau Divers: Albert Falco (Chief Diver/cameraman), Raymond Coll (cameraman), Bernard Delmotte, Patrick Delmotte, Marc Zonza, Ivan...

hmhsbritannic.weebly.com

 

[Nick_Radov]

Let me just briefly quote some famous and highly respected divers on deep air dives.
1947 Frederi Dumas 308 ft
1961 Hal Watts 350 ft
1965 Tom Mount 360 ft
1971 Sheck Exley 466 ft
1993 Bret Gillian 475 ft

When was Bret Gilliam considered to be "highly respected"? My understanding is that he was always considered to be more of a clown and an embarrassment to the sport. But I'm a relative newcomer, so perhaps I'm missing some context.

The Call of the Wah-Wah

The lingering legacy of DEEP AIR in the era of MIX—from the aquaCORPS archives

indepthmag.com

 

[CG43]

Hello Nick_Radov

Thanks for the link to “ The Call of the Wah-Wah .
Very interesting to read .

Yet the accepted standards are not malleable, said an industry insider. “The 1.45 atm limit is not there for everyone except Bret Gilliam and Joe Odom,” he said. “The limit is there for all divers.”

The answer from Joe Odon :
“Are we creating a climate of ‘Do as I say, not as I do?’ Well, of course, but that’s the way it’s been since day one.”—Joe Odom

I am not very surprised that there are divers who like to drink more than just one martini.
Shall we ascent to 160 feet ? What is this , one beer ?

 

[eightytwenty]

Yes, yes, I have heard all this, many times before. I can also quote may divers who have lost their lives on rebreathers. The ratio of rebreather deaths to open circuit scuba deaths has been quoted as about 5 to10 rebreather deaths to every single open circuit scuba death.

Certainly, I have dived with some individuals who have experienced narcosis at 100 feet. In fact, I rescued a buddy diver who was narked out (asleep on the bottom with his eyes open) at the end of a 25 mins deco dive at 140 feet on air.

Consequently, for some people narcosis is a serious problem. However, some individuals can function despite narcosis at considerable depth.

Whether you use a rebreather or open circuit scuba, it is a question of analysis of dive site conditions, individual susceptibility/capability with narcosis, individual perception of risk, good risk assessment to identify and mitigate problems and proper dive planning.

Also, trimix is not easily available all over the world. In some cool remote locations, all you can find is air. Therefore, if you have a rebreather you may have to use air as a diluent.

In conclusion, whether you use a rebreather on trimix or open circuit on air to 160 feet, both approaches present risks. It is your individual choice based on sound risk assessment. To quote Sheck Exley "what works, works".

Let me just briefly quote some famous and highly respected divers on deep air dives.
1947 Frederi Dumas 308 ft
1961 Hal Watts 350 ft
1965 Tom Mount 360 ft
1971 Sheck Exley 466 ft
1993 Bret Gillian 475 ft

Rob Palmer
Chris and Chrissy Rouse
Rob Parker
Maurice Fargues

What's your point? Exley died alone chasing depth, breaking the very rules he laid out. Gilliam and Mount (read: Mouth) are looked at more as laughingstocks than anything else these days, and the very same day Frederic Dumas did his 308-foot dive, Maurice Fargues died trying to dive to 390 feet.

Science moved past deep air decades ago, the only people who still cling to it are chest beating dilettantes. These days, every time you hear someone explaining why they dive deep air, it comes bundled with a healthy helping of mental gymnastics as to why they're choosing to dive what they dive. I think some people are just afraid of change.

 

[eightytwenty]

When was Bret Gilliam considered to be "highly respected"? My understanding is that he was always considered to be more of a clown and an embarrassment to the sport. But I'm a relative newcomer, so perhaps I'm missing some context.

The Call of the Wah-Wah

The lingering legacy of DEEP AIR in the era of MIX—from the aquaCORPS archives

indepthmag.com

I think it depends on how much you like deep air bounce dives and fake shark attack stories.

 

[old frogman]

So, in the dive shop, we were having this discussion about a deep cavern dive where the dive plan was 160ft... which is less dangerous?

Is it safer to dive with a little narcosis on a simpler system (sidemount on air with o2 deco), or is it safer to be clear headed on CCR (a rig that is trying to kill you)? (Assume the diver is trained and comfortable with both.)

Why the question: because helium is expensive, so open circuit trimix is not a realistic option.

I could not find statistics about this, so I am asking the question.

Gentlemen, let's get back to the basic question (as above). He did not state cave diving application, which in itself is a high-risk pursuit and if you mix rebreathers with cave diving you increase the risk geometrically (let alone add hydrogen to the equation which puts risk to an astronomical level). If you are that way inclined, all the power to you.

Assuming that this gentleman referred to just general open water diving to 160 feet, let's refer to the following references:

USN Dive Manual. I recall reading that air diving can be authorised to 190 feet on air.

Some commercial diving authorities (Industrial and construction) authorise diving down to 165 feet on air.

In the end it is a matter of balancing risk with opportunity and what you are comfortable with.

If you think rebreather and nitrox is the bees knees, I am happy for you. Conversely if you think open circuit scuba with air is the way to go, I am equally happy for you.

 

[inquis]

Assuming that this gentleman referred to just general open water diving to 160 feet

The OP (and your quote) contradicts your assumption.