An age-old question: ways to 60m.

[LFMarm]

Gas selection is irrelevant, 100 000dives/1 fatality in rec diving and 6000-10000 dives/1 fatality in CCR. These are the odds.

This is an oranges and apples comparison. If you normalize for risk exposure of dives (e.g., PrT — avg depth x square root of time) I assume the split would be different. Tech dives are inherently more dangerous than NDL dives in OW, this is why tech diving requires equipment, procedures, and training to mitigate the risk.

Deep diving on air on a single tank is more risky than deep diving (to the same depth for the same time) with appropriate equipment, gases, and procedures.

Risk is not zero for either option but it’s lower in the second one. This also doesn’t mean that diving with the first option will result is an accident every time, as testified by team deep air in this thread. But let’s please stop asserting that the risk is the same just because it worked in the past.

 

[Kay Dee]

@Kay Dee
Still out looking for WWII wrecks without Empress and the Capt?

No, not at present.

 

[Kay Dee]

The issue with gas density in deep air has nothing to do with overbreathing the regs. It's about the internal airway resistance within your lungs. At 60m, your lungs cannot achieve the same maximum SAC rate with air as with trimix, or with air at 30m. If high workload happens (planned or unexpected), your lungs cannot get rid of CO2 fast enough at 60m on air, no matter what reg you use. That's one of the things we didn't know in 2000.

I hear what you are saying re not expelling the Co2 fast enough, but I overhear divers around the traps talking of being surprised in finding their regs hard to breath at depth, and that (sub standard equipment for depth, i.e. regs in this example) problem is part of the reason that Co2 is building up in the first place. And note that I said 'part of' not 'the only'.

 

[old frogman]

This is an oranges and apples comparison. If you normalize for risk exposure of dives (e.g., PrT — avg depth x square root of time) I assume the split would be different. Tech dives are inherently more dangerous than NDL dives in OW, this is why tech diving requires equipment, procedures, and training to mitigate the risk.

Deep diving in air on a single tank is more risky than deep diving (to the same depth for the same time) with appropriate equipment, gases, and procedures.

Risk is not zero for either option but it’s lower in the second one. This also doesn’t mean that diving with the first option will result is an accident every time, as testified by team deep air in this thread. But let’s please stop asserting that the risk is the same just because it worked in the past.

Clearly you cannot function with narcosis beyond 30 to 40 metres depth. I respect that and I acknowledge that in your situation trimix is a wise option if used in OC mode. However, trimix in CCR mode is just swapping one risk for another.

Fatality rate per 100,000 dives
CCR diving 2-4
Skydiving 0.23-0.39 (as in freefall parachuting)
OC diving 0.2-0.4

Deep air diving to me is 60 metres or 200 feet max.

 

[Kay Dee]

Deep diving in air on a single tank is more risky than deep diving (to the same depth for the same time) with appropriate equipment, gases, and procedures.

Deep diving on a single tank using any gas is not only risky, it is stupid. Not saying you do it, just clarifying what you said.

 

[Kay Dee]

Clearly you cannot function with narcosis beyond 30 to 40 metres depth.

Who are you referring to here? The poster you replied to I assume?

However, trimix in CCR mode is just swapping one risk for another.

Well, sticking your head underwater is a risk to start with. I think it all gets back to ones level of 'risk acceptance' as opposed to just doing 'stupid things'.

Deep air diving to me is 60 metres or 200 feet max.

Agreed 60, 65m max, but I would much rather be on trimix and a CCR.

To take a line from Toby Keith's song "Weed With Willie";
"Well don't knock it till you've tried it.
And I've tried it my friend."

 

[old frogman]

Who are you referring to here? The poster you replied to I assume?

Well, sticking your head underwater is a risk to start with. I think it all gets back to ones level of 'risk acceptance' as opposed to just doing 'stupid things'.

Agreed 60, 65m max, but I would much rather be on trimix and a CCR.

To take a line from Toby Keith's song "Weed With Willie";
"Well don't knock it till you've tried it.
And I've tried it my friend."

I agree with don't knock it until you tried it.

 

[Wibble]

Clearly you cannot function with narcosis beyond 30 to 40 metres depth. I respect that and I acknowledge that in your situation trimix is a wise option if used in OC mode. However, trimix in CCR mode is just swapping one risk for another.

Fatality rate per 100,000 dives
CCR diving 2-4
Skydiving 0.23-0.39 (as in freefall parachuting)
OC diving 0.2-0.4

Deep air diving to me is 60 metres or 200 feet max.

And fatality rates for OC technical diving?

OC diving is massively biased to short, shallow NDL dives, i.e. easy and simple, whereas CCR diving will generally include some—often substantial—decompression, therefore are technical dives.

Vis-a-vis recreational DiveMasters commonly have many thousands of dives yet highly experienced technical divers rarely have more than a thousand dives, although will have a considerably higher average dive duration than recreational divers.

From my Shearwater dive logs since 2017 (never imported earlier dives from the Suunto), my 310 OC dives totalling 300 hours with average dive time of 55 minutes (longest dive 2h22, average depth 21m, deepest 74m), whereas my 277 CCR dives totalling 400 hours, average is 1h25 (longest 4h, average depth 33m, deepest 77m). My OC diving was mainly technical profile with mixed gases, so not a typical recreational profile as found on typical recreational boats that most people will dive.

Alas, I’ve known several people who’ve died whilst diving or subsequently due to a dive, all were technical profiles. Technical diving is unforgiving at depth and places great stress on the body, hence there’s very few technical divers over the age of 70.

 

[LFMarm]

Deep diving on a single tank using any gas is not only risky, it is stupid. Not saying you do it, just clarifying what you said.

Fully agree. Just worse with air.

 

[old frogman]

And fatality rates for OC technical diving?

OC diving is massively biased to short, shallow NDL dives whereas CCR diving will generally include some—often substantial—decompression, therefore are technical dives.

Vis-a-vis recreational DiveMasters commonly have many thousands of dives yet highly experienced technical divers rarely have more than a thousand dives, although will have a considerably higher average dive duration than recreational divers.

From my Shearwater dive logs since 2017 (never imported earlier dives from the Suunto), my 310 OC dives totalling 300 hours with average dive time of 55 minutes (longest dive 2h22, average depth 21m, deepest 74m), whereas my 277 CCR dives totalling 400 hours average is 1h25 (longest 4h, average depth 33m, deepest 77m). My OC diving was mainly technical profile with mixed gases, so not a typical recreational profile as found on typical recreational boats that most people will dive.

Alas, I’ve known several people who’ve died whilst diving or subsequently due to a dive, all were technical profiles. Technical diving is unforgiving at depth and places great stress on the body, hence there’s very few technical divers over the age of 70.

I am not sure what point you are trying to make. But from what you are saying, regarding OC versus CCR, to me appears to actually support the stats above which are based on a fatality rate per 100,000. This rate is a staple metric in epidemiology. It is used by professionals to compare the rate of fatality across different discipline, geographic regions, populations, etc.