Riding GF99 instead of mandatory/safety stops

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Agreed, you do not have to change the GF during the dive. However, why does the shearwater computer have a facility to change the GF during the dive?
They only allow you to adjust the GFhi because once you've started the deco the GFlow is in the past.

And for the same reason they show you surfGF and GF99. So you can add time and surface with a lower GF. If you set your GFhi to 85 at the surface, have a very intense dive, you can edit it while you wait on your deco to GFhi 80 and surface more conservatively. Or looks at GF99 and wait until its below 80. Resetting it lower just allows you to see how much longer you need to hang
 
Show me one study that actually put recreational <NDL divers on O2 at a safety stop for 3 to 5 minutes and showed a reduced incidence of DCS. Heck even a doppler study or with rats, rabbitss or beagles. It's not proven to be relevant - in part because the rates of DCS for recreational divers are already extremely small and measuring the difference (if it even exists) between 1 in 7,000 dives and 1 in 8,000 dives is ridiculously expensive and not worth anyone paying for. And the actual time on O2 at a safety stop is similarly tiny.

As pointed out to you MANY times before, whatever value 100% offers during a 3 minute safety stop is functionally reproducible by doing a 6 minute safety stop. Although neither is going to substantively change your overall gas load in the controlling tissues and thus the net rate of DCS is going to remain within the margin of error anyway.

https://www.technicaldivingindia.com/files/TechnicalDivingIndia-OxygenWindow-Final.pdf

Oxygen Window - Alert Diver Magazine | DAN Europe

Oxygen Window: Explanation and Purpose?

The Oxygen Window

 
 
And you are claiming that this has a significant effect for a 3-minute safety stop on a recreational dive?

I have been trying not to rise to the bait of your inane questions or statements; but without success....I specifically said that my safety stops when using EAN40 to avail myself to the oxygen window would be extended and never stated "3mins" as my safety stop time....but you knew that...if anything can me modified on the fly during a profile to lessen the chance of tissue damage extending the shallow safety stop time, especially if using higher % of oxygen, will help prevent that damage. Otherwise why are SSs used?

Direct answer....yes [read articles] breathing a higher concentration of oxygen enhances, improves, the removal of inert gases such as nitrogen in my case since I only dive 21% air from the tissues.....you use "significant" as a modifier to your supposition that use of oxygen with your '3min' construct on any dive will not result in 'significant' removal of nitrogen....each dive is unique as are the parameters/variables that can induce injury to the diver....significant is anything that can reduce the probability of injury....diving is a matter of inches not miles; small details matter. There are no absolutes in preventing injuries to divers but every little increment just might keep the diver safe. Like "Old" stated, as have I, you never eliminate risk you only can hopefully reduce the risk.

Of all the chatter, the use of the oxygen window to lessen the probability of DCS or asymptomatic injuries is accepted as true...same reason decompression chamber use 100% oxygen as part of their treatment protocols.

One thing for certain, today's paradigms will change over time. But currently, understanding and utilizing the oxygen window benefits during an extended SS while on higher % of oxygen is a gold standard.

But hey, do whatever you choose on your dives....all about individual choice and concurrent responsibility.
 
I have been trying not to rise to the bait of your inane questions or statements; but without success....I specifically said that my safety stops when using EAN40 to avail myself to the oxygen window would be extended and never stated "3mins" as my safety stop time....but you knew that...if anything can me modified on the fly during a profile to lessen the chance of tissue damage extending the shallow safety stop time, especially if using higher % of oxygen, will help prevent that damage. Otherwise why are SSs used?

Direct answer....yes [read articles] breathing a higher concentration of oxygen enhances, improves, the removal of inert gases such as nitrogen in my case since I only dive 21% air from the tissues.....you use "significant" as a modifier to your supposition that use of oxygen with your '3min' construct on any dive will not result in 'significant' removal of nitrogen....each dive is unique as are the parameters/variables that can induce injury to the diver....significant is anything that can reduce the probability of injury....diving is a matter of inches not miles; small details matter. There are no absolutes in preventing injuries to divers but every little increment just might keep the diver safe. Like "Old" stated, as have I, you never eliminate risk you only can hopefully reduce the risk.

Of all the chatter, the use of the oxygen window to lessen the probability of DCS or asymptomatic injuries is accepted as true...same reason decompression chamber use 100% oxygen as part of their treatment protocols.

One thing for certain, today's paradigms will change over time. But currently, understanding and utilizing the oxygen window benefits during an extended SS while on higher % of oxygen is a gold standard.

But hey, do whatever you choose on your dives....all about individual choice and concurrent responsibility.
You are missing the point of the oxygen window. The point is that the use of 100% O2 means 0% N2, so the nitrogen gradient between what is in your tissues and what is in your breathing gas is very large, and thus helpful in off-gassing. But the gradient using 40% O2 is much smaller, therefore much less helpful, if helpful at all.
 
If you have access to 40% why dive 21%?
Guess not privy to my other explanations of how I would use EAN40. I dive deeper than prudent with EAN of any %. Will hang a bottle of EAN40 [easy to get fills and no need to oxygen wash gear at 40%] at my safety stops. SS depth will depend on altitude and planning on extending time of SS dependent on max Z of dive. Limiter to SS time will be gas available and if hypothermic; longer the better.

Old school, less gear, less chance of failure of gear or in decisions making...definitely trying to keep it simple while buffering against further tissue damage [existing injuries for decades of diving].
 
I have been trying not to rise to the bait of your inane questions or statements; but without success....I specifically said that my safety stops when using EAN40 to avail myself to the oxygen window would be extended and never stated "3mins" as my safety stop time....but you knew that...if anything can me modified on the fly during a profile to lessen the chance of tissue damage extending the shallow safety stop time, especially if using higher % of oxygen, will help prevent that damage. Otherwise why are SSs used?
If you're properly trained in gas switching and staged decompression then feel free to do that, it won't hurt. But the fact that you're asking these basic questions online leads me to suspect that you lack this training and might be taking risks that you don't really understand with things like gas switching protocols and oxygen exposure limits. Nitrox 40 would be an odd (non-standard) and rather pointless choice of deco gas at the typical "safety stop" depth of about 15 ft / 5 m.

If you want to get into this type of entry-level technical diving then the GUE Master Diver (Rec 3) course could be a good option. It covers skills pretty similar to what you want to do including switching to a nitrox mix on ascent. And it should get you clear on the basics of modern deco theory. We can't teach you how to do this stuff safely on a ScubaBoard thread.
 

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