Not diving to greater than 30m/100ft unless with helium

[100days-a-year]

At 130' decompression will certainly be a factor using modern computers and by dive 3 it can be a huge issue.
I've dove quite a few computers side by side at those depths and deco obligation can be different by a factor of 10 so gas and time management are a bit more complicated than AOW teaches.

Certainly not rocket science but far beyond most divers desire or ability to deal with.Most of the non-professionals I dive with want to jump in,swim around and look at cool stuff and head back whenever they want or when they reach their personal turn point.Not deal with much planning, deco gas or stops other that a cursory safety stop.

 

[DivemasterDennis]

There is a lot of difference from one diver to the next concerning when, and if, they experience narcosis. Individual physiology, number of hours of bottom time at depth, how "hyper" you are on the dive, and probably other factors impact. I have heard some say speed of descent can be a factor. Both Debbie and I have scores of dives on air between 100 and 130 feet, without issue. No narcosis, no DCI, no issues. We plan no decompression dives, and follow our plan. Susceptibility to narcosis is a difference, not a weakness. I like Akimbo's post- know (learn) your own limitations and susceptibilities.
DivemasterDennis

 

[Patoux01]

Without the benefit of personally knowing you or your diving history, your posts suggest that you are a prudent and experienced diver. 50M/164’ was the suggested recreational depth limit in Europe for a long time.

I know at least 2 countries here where 60m is still in the rec range... ie you don't need any trimix, or O2 cert to do dives to 60m.

 

[boulderjohn]

I know at least 2 countries here where 60m is still in the rec range... ie you don't need any trimix, or O2 cert to do dives to 60m.

I don't know what you mean by this. I don't know many countries that have any laws on diving depths or breathing mixes. I think those rules are up to individuals or operators. When I dived on Andros Island in the Bahamas, the operator routinely took OW divers to 150 feet on single tanks of air if they wanted to go there.

 

[Kevrumbo]

Use Helium at depth when you need cognitive clarity & N2 Narcosis mitigation whilst navigating/laying line inside an overhead such as a cave or wreck; also use He when you expect physically challenging conditions such as strong currents to work against, in order to minimize exertion Hypercapnia & extreme CO2 Narcosis.

Here's a practical example where having a robust easier to breath 18/45 Trimix gave this group of Tech Divers an "error margin" (e.g. CO2 retention moderation and a deeper MOD margin to deal with a strong downcurrent) and note in this incident, no mention of debilitating narcosis:

[url]http://www.scubaboard.com/forums/near-misses-and-lessons-learned/387384-minimum-gas-underwater-climbing-drifting-away.html

[/URL](What would have happened if they used Air?)

 

[1978davidw]

Has anyone here ever used CO2 scrubbers in their post compressor filtration system? I have my own compressor set up and i pack my own filters. right after my hopcalite which turns CO to CO2 i have a CO2 scrubber. This has helped a lot with headaches/narcosis as my CO2 levels are less than 10ppm in my air coming off my home compressor. For anyone doing deep dives i recomend this.

 

[Kevrumbo]

Has anyone here ever used CO2 scrubbers in their post compressor filtration system? I have my own compressor set up and i pack my own filters. right after my hopcalite which turns CO to CO2 i have a CO2 scrubber. This has helped a lot with headaches/narcosis as my CO2 levels are less than 10ppm in my air coming off my home compressor. For anyone doing deep dives i recomend this.

Assuming a compliant and standard clean Air fill from a reputable Dive Shop, the actual problem is still with metabolic CO2 generation and physiological limitations of the human respiratory & circulatory system when it comes to Scuba in a immersed wet hyperbaric environment. Having a CO2 scrubbed and a hyper-filtered air source described above can't hurt, but doesn't really offer any practical advantage at all for work at deep depth. . . If you cannot expel metabolic CO2 efficiently because of physical exertion, or inadequate exhalation due to skip breathing, you will develop symptoms of Hypercapnia regardless of how well your source air has been scrubbed or filtered free of CO2 from your compressor.

 

[kathydee]

One of the more interesting experiments I've done underwater was switching from 32% to 18/45 @ 100 feet for a few minutes,then switching back -- to test the difference in awareness. For me, the difference was significant, but YMMV.

 

[Lorenzoid]

One of the more interesting experiments I've done underwater was switching from 32% to 18/45 @ 100 feet for a few minutes,then switching back -- to test the difference in awareness. For me, the difference was significant, but YMMV.

I was just wondering yesterday about such experiments. It sure would be interesting to see this done in a more scientific manner--you know, more than a few data points, and having the diver perform some tasks to objectively measure awareness. Oh, and make sure the test subjectsare not biased by what their agency teaches.

It's interesting that you say you noticed a difference even at just 100 feet. It occurred to me that the people who are qualified to perform this experiment are likely to have breathing skills well in hand--thus taking CO2 at least partly out of the equation. When we rec-only divers say we believe we feel less alert at 100 feet, the immediate reaction from the tech community is that we're probably not breathing as well as we could.

 

[MXGratefulDiver]

One of the more interesting experiments I've done underwater was switching from 32% to 18/45 @ 100 feet for a few minutes,then switching back -- to test the difference in awareness. For me, the difference was significant, but YMMV.

I've done the same test at 100 fsw ... but with 25/25. Even that was significantly noticeable, despite the fact that I would've sworn beforehand that I am not narced on EAN32 at that depth ...

... Bob (Grateful Diver)