Mixed buddies (air/Nitrox)

[SATurner]

Is there an issue if two divers are using different gases in their tanks on a dive? For example one has air, one has Nitrox and an out of air event or some other catastrophic failure requiring shared air.

Going a step farther if the answer above is no, what if there are 4 dives planned for the day, two have been successful. On the third dive, the Nitrox diver has the failure and goes over to air. Failure occurs close to air NDL, but we'll short of Nitrox NDL. Should the 4th dive be scrubbed by the Nitrox diver?

Are there any times you can think of where pairing a person on air with a person on Nitrox should or shouldn't be paired together?

I also struggled with whether to put this in basic or advanced...

 

[Tracy]

No. An out of air scenario involving gas sharing is an ascent to the surface. Not carrying on the dive for another 20 minutes. The time frame of use isn't going to make a difference.

 

[SATurner]

@Tracy, thank you. I didn't intend to suggest a continuance of the dive after the incident, but was instead trying to "stack" the deck to potentially cause the Nitrox diver to rethink the 4th dive due to the "air" contamination.

Your answer drags me back to k.i.s.s. keep it simple Seth! The Nitrox diver was well below Nitrox NDL so the 4th dive is possible.

Do any adjustments need to be made when planning the fourth dive by the Nitrox diver or is it just a shortened bottom time going into the next dive planning?

 

[Searcaigh]

Is there an issue if two divers are using different gases in their tanks on a dive? For example one has air, one has Nitrox and an out of air event or some other catastrophic failure requiring shared air.

No

The Nitrox diver however will need to follow the air diver's NDL if they are buddies unless the Nitrox diver plans to solo after the air diver has surfaced on say a 30m square profile dive.

However if diving a reef that goes shallow there probably will not be too much difference on the NDLs of both divers once shallower than 10m.

In an OOA situation of either diver you're both ascending and finishing the dive.

Going a step farther if the answer above is no, what if there are 4 dives planned for the day, two have been successful. On the third dive, the Nitrox diver has the failure and goes over to air. Failure occurs close to air NDL, but we'll short of Nitrox NDL. Should the 4th dive be scrubbed by the Nitrox diver?

This is probably a more advanced question, and the answer is probably depends on depths and times of the dives.

Pre-Nitrox days on a trip to the Maldives I did five dives a day for six days (1998), but as the day moved on I was not exceeding 10m on the afternoon dives.

Are there any times you can think of where pairing a person on air with a person on Nitrox should or shouldn't be paired together?

Again, depends on the planned dive depth.

 

[Tracy]

@Tracy, thank you. I didn't intend to suggest a continuance of the dive after the incident, but was instead trying to "stack" the deck to potentially cause the Nitrox diver to rethink the 4th dive due to the "air" contamination.

Your answer drags me back to k.i.s.s. keep it simple Seth! The Nitrox diver was well below Nitrox NDL so the 4th dive is possible.

Do any adjustments need to be made when planning the fourth dive by the Nitrox diver or is it just a shortened bottom time going into the next dive planning?

I am following now.
My honest opinion, in the realm of recreational diving, if a diver runs out of breathing gas, whatever it may be. They are definitely done for the day. So there wouldn't be any planning concerns for the next dive.

 

[formernuke]

I am following now.
My honest opinion, in the realm of recreational diving, if a diver runs out of breathing gas, whatever it may be. They are definitely done for the day. So there wouldn't be any planning concerns for the next dive.

To me it would depend on why they ran out.

OP. In the recreational world it really doesn't matter if the person on nitrox has to use someone on airs octo. At that point both divers are coming up hopefully at 30 feet a minute. Once at 15 feet if they have sufficient air making the 3 minute stop and surfacing. The amount of extra nitrogen is not sufficient to really matter.

 

[jborg]

All that said, a nitrox/air buddy team is generally not a great pairing. Presumably, the nitrox diver uses nitrox for a reason, which would be tricky to gain the advantage of when paired with a buddy on air.

 

[formernuke]

All that said, a nitrox/air buddy team is generally not a great pairing. Presumably, the nitrox diver uses nitrox for a reason, which would be tricky to gain the advantage of when paired with a buddy on air.

Not true, when I was in Roatan a lot of the people were only doing the 3 boat dives per day. I was doing 5 dives a day, one of the reasons I was using nitrox.

 

[jborg]

I concede your "different dive plans over the long term" and stand by my "generally".

 

[Gareth J]

The rules are simple for a Nitrox / Air buddy pair.

The Air diver MUST respect the MOD of the Nitrox diver, and understand that this must never be broken.
The Nitrox diver MUST follow the air divers decompression schedule (either NDL or decompression).