Same-day switching between air and EAN

[love2godeep]

Does anyone know of any research that has been done on whether or not it is safe to switch between air and Nitrox on subsequent dives on the same day?

Excuse-moi if this has already been discussed. I looked for it but didn't see anything.

 

[Dr. Doug Ebersole]

There are no safety issues from breathing different gas mixtures -- technical divers often change mixes multiple times during a single dive. It's just a nitrogen loading issue and a maximum depth issue (oxygen toxicity). There is no reason not to switch between air and nitrox during the day -- just make sure you switch your dive computer to match.

 

[love2godeep]

There are no safety issues from breathing different gas mixtures -- technical divers often change mixes multiple times during a single dive. It's just a nitrogen loading issue and a maximum depth issue (oxygen toxicity). There is no reason not to switch between air and nitrox during the day -- just make sure you switch your dive computer to match.

That's what I always thought but an ad I got in the mail for a dive magazine said that they had new information on this. I haven't subscribed to the mag, but I was curious if something has come up.

 

[Damselfish]

What magazine is that?

 

[Charlie99]

The only remote possibility of problems I could see is that some computers don't track CNS and whole body O2 dosage when in the air mode. If you do a deep air dive first, then switch over to nitrox you would be showing lower O2 dosage than you really have experienced. If you have computer that doesn't track O2 in air mode (some track but don't display), all you have to do is to start off in nitrox mode and enter 21% for the air dives.

 

[Damselfish]

The only remote possibility of problems I could see is that some computers don't track CNS and whole body O2 dosage when in the air mode. If you do a deep air dive first, then switch over to nitrox you would be showing lower O2 dosage than you really have experienced. If you have computer that doesn't track O2 in air mode (some track but don't display), all you have to do is to start off in nitrox mode and enter 21% for the air dives.

some computers won't even let you switch modes - until the thing clears you're stuck in whatever mode you started with. So if you plan on diving nitrox you have to set to Nitrox 21 when diving air.

 

[Blackwood]

You can switch back and forth. As was mentioned, if you are computer diving only, it may not track your O2 clock.

 

[String]

As others have said, there is no real danger switching (Air is just nitrox-21 anyway). However if you use a computer in air mode they tend not to track whole body or CNS o2 exposure whereas in nitrox mode they do.
Therefore the only "risk" is misapplication of a computer. Some will lock out for 24hrs after a mode change to get around this issue.

I just keep my computer in nitrox mode and set it to 21% for air to avoid coming across this.

 

[love2godeep]

What magazine is that?

Undercurrents.

 

[SStrecker]

some computers won't even let you switch modes - until the thing clears you're stuck in whatever mode you started with. So if you plan on diving nitrox you have to set to Nitrox 21 when diving air.

That strategy works quite effectively with Aeris, Oceanic and several other models of dive computers, where you are stuck in an EANx mode lock down.

Alternatively, you could use the Nitrox as a safety factor, treating it as a standard air fill but observing the strict MOD maximum operating/oxygen depth limitations for those dives.

Personally, I would recommend, playing it straight, with the dive computer (and /or tables) settings and address each dive with it's corresponding correct EANx values.