EAN versus "no-Fly" delay

[tbone1004]

@BRT why do you know that is not true?

 

[Remy B.]

I have taken many times flights with Surface time of 12hrs to 16hrs after diving, but if I do so I use EAN 32, and I stay shallow, so the NDL are high, not saying that it is the right thing to do, the recommended is still the 24hr wait time

I never use just air knowing I will fly the next day, but I always calculated the time so at least 12Hrs had pass.

 

[redacted]

when diving deeper is the risk of DCS reduced, increased or does it stay the same?

Well, YES, of course.

 

[BRT]

@BRT why do you know that is not true?

Because you are trying to tell us that if you treat a ndl dive like a decompression dive and stay underwater "decompressing" longer than you need to, you will have less nitrogen in your body than if you just came to the surface at the end of the dive. This is the same as saying if you spend part of your surface interval diving shallow you are lowering your nitrogen level and can do the 2nd dive sooner.

 

[Chris12day]

NO
it does nothing to reduce the chance of a DCS hit if you are setting your computer to that mix. If you tell your computer that you are diving nitrox 32, and you are diving nitrox 32, and dive to NDL it has the same risk as if you were diving air and told it you were diving air. It only helps to reduce the risk if you dive EAN and tell the computer that you are diving air, or some mix that is less enriched

I was responding to "safety stops". We do "safety stops", independent of the gas used, to reduce the chance of a DCS hit. This of course assumes that you do not go into DECO, then it is a mandatory stop and not a "suggested" stop.

 

[Bob DBF]

there is actually a way to do it....
*disclaimer, this is not endorsed or recommended by anyone, including myself and any agencies that I am an instructor for, including DAN. Please do NOT try this*

Typical cabin pressure will max out at ~8000 ft. This is roughly 3/4 of an atmosphere. If you treat your last dive as an altitude dive at 8000ft, then you can basically fly immediately after the dive if you plan your decompression or NDL's appropriately. Why? you're basically saying that instead of surfacing at sea level, you are conducting the dive as if you were at the cabin pressure of the plane. Your NDL's will be short or your deco will be long, but it is possible to basically "trick" your body into decompressing to a point that it will not supersaturate at altitude. This is no different than the guys that live in the mountains and dive at sea level.

I'd really need a spectacular dive to do that, and I dive on the 7000' table for some of my dives. My issue is that the cabin pressure is 8000' and a commercial jetliner is flying well over 25,000 feet, one problem with cabin pressure... I'll wait the 24 hours, and on my non dive vacations when diving I wait a couple of days.

Because you are trying to tell us that if you treat a ndl dive like a decompression dive and stay underwater "decompressing" longer than you need to, you will have less nitrogen in your body than if you just came to the surface at the end of the dive.

If you are diving EAN at shallow depths, yes you will, unless you are breathing O2 on the surface after the dive. File it under "all dives are decompression dives".



Bob

 

[BRT]

I'd really need a spectacular dive to do that, and I dive on the 7000' table for some of my dives. My issue is that the cabin pressure is 8000' and a commercial jetliner is flying well over 25,000 feet, one problem with cabin pressure... I'll wait the 24 hours, and on my non dive vacations when diving I wait a couple of days.



If you are diving EAN at shallow depths, yes you will, unless you are breathing O2 on the surface after the dive. File it under "all dives are decompression dives".



Bob

Any EAN? Any shallow depth? For some reason we don't go shallow breathing nitrox and then just hook up a new tank and dive another dive. Let me see. 32% at 10 feet would be a PP of nitrogen of .89. Think you gain anything over the surface PP of .79? Your best nitrogen removal if you don't have a high percentage of O2 to breath is to go to the surface. If you do have O2 to breath go to the surface and breath it.

 

[RainPilot]

I downloaded the NOAA fly after dive tables the other day, there is a marked difference using EAN than air.

I agree with @tbone1004 that a longer deco stop will reduce your N2 loading faster than just surfacing. There's a reason it's called accelerated deco and as long as you are breathing a PPN2 lower than 0.80 you will be better off than on the surface.

GI3 used to brag about ending his dives so clean he could go fly immediately even after VERY long deco dives. I'm not quite as good an offgasser as that though.

 

[BRT]

I downloaded the NOAA fly after dive tables the other day, there is a marked difference using EAN than air.

I agree with @tbone1004 that a longer deco stop will reduce your N2 loading faster than just surfacing. There's a reason it's called accelerated deco and as long as you are breathing a PPN2 lower than 0.80 you will be better off than on the surface.

GI3 used to brag about ending his dives so clean he could go fly immediately even after VERY long deco dives. I'm not quite as good an offgasser as that though.

If you are breathing a PPN2 lower than at the surface you will be decompressing faster than on the surface. 32% at 10 feet does not do that. If you want to gain more go to the surface and breathe your high O2 mix.

 

[tbone1004]

@BRT, I was not talking about offgassing faster. You don't have to have your tissues at "surface" levels in order to safely fly. It is recommended, hence the 12-16-24 hour intervals depending on the tables you subscribe to, but as long as the tissues when exposed to 0.75 ata are not exceeding their theoretical limits, i.e. pretending to conduct your dive as if you were at an 8000ft altitude and stick to NDL's then you should be OK. I'm not talking about getting your tissues to the same point or lower as your surface tissue loading. That requires pure O2, and a LOT of it. All I'm talking about is basically diving at sea level, as if you were conducting an 8,000ft altitude dive. Your NDL's will be very short, but it is possible.

Again, not recommending it, I do it, I have lots of friends that do it, and if you have O2 that you can accelerate your deco it just means you can dive longer or fly sooner.