Deep Diving on Nitrox question

[MXGratefulDiver]

FWIW - when I went to Coz I stayed and dived with Aldora. At the time ... and I suspect still ... they recommended EAN28 for Devil's Throat. And yes, they wanted everyone on the same mix to make managing the dive easier.

Having stayed there, and knowing their reputation for diving safety, I have a hard time believing they're pushing a 130-foot dive on EAN32. Something about this story isn't adding up.

... Bob (Grateful Diver)

 

[scubadada]

FWIW - when I went to Coz I stayed and dived with Aldora. At the time ... and I suspect still ... they recommended EAN28 for Devil's Throat. And yes, they wanted everyone on the same mix to make managing the dive easier.

Having stayed there, and knowing their reputation for diving safety, I have a hard time believing they're pushing a 130-foot dive on EAN32. Something about this story isn't adding up.

... Bob (Grateful Diver)

In 2006, my son and I did Devil's Throat with Aldora on air. It was still a 65 minute, multilevel dive with a max depth of 127 feet and an average depth of 58 feet. We had a couple of minutes of deco.

Back then, all of our 1st, and deeper, dives were on air. Our 2nd dives were all on 32%. I'm not sure they had the ready availability of other mixes then. 28% would be perfect for this dive with a MOD of 132 feet.

 

[RandomGuy1]

For me I wouldn't have done it. I realize that diving physiological is a huge grey area, but you have to draw a line somewhere. I calculate my MOD based on 1.4 and that is what I stick to. Was it really dangerous to spend a few minutes below MOD. Probably not, at least until you have a problem, then it is one more thing to have to worry about.

 

[orange_diver]

I've done the Throat a few times with multiple operators and always on air as per my request and with a steel 120. One time the DM stopped to spear a couple of lion fish at 130' and had a bit of trouble getting them into his container so we were at that depth for 5 minutes.

Turned into a light deco dive but it was a small group of 3 customers and we all happened to be technically trained so not a big deal. So... although it may be a diver's intention to not stay long at 130' they may wind up there to deal with a situation and the O2 clock starts ticking... And that's not even an emergency scenario with raised SAC rates.

And for the record there are way better/more fun dives in Coz that don't get below 60'...

 

[k4kafka]

Don

Doen't your download of your log give you average depth and calculate your RMV? The average depth is required to make that calculation. An example from Oceanic Oceanlog:
View attachment 379978

Don't download from my computer.

 

[k4kafka]

I've done the Throat a few times with multiple operators and always on air as per my request and with a steel 120. One time the DM stopped to spear a couple of lion fish at 130' and had a bit of trouble getting them into his container so we were at that depth for 5 minutes.

Turned into a light deco dive but it was a small group of 3 customers and we all happened to be technically trained so not a big deal. So... although it may be a diver's intention to not stay long at 130' they may wind up there to deal with a situation and the O2 clock starts ticking... And that's not even an emergency scenario with raised SAC rates.

And for the record there are way better/more fun dives in Coz that don't get below 60'...

All good points to consider ! Which was the reason for my post.

 

[k4kafka]

FWIW - when I went to Coz I stayed and dived with Aldora. At the time ... and I suspect still ... they recommended EAN28 for Devil's Throat. And yes, they wanted everyone on the same mix to make managing the dive easier.

Having stayed there, and knowing their reputation for diving safety, I have a hard time believing they're pushing a 130-foot dive on EAN32. Something about this story isn't adding up.

... Bob (Grateful Diver)

This was my third year diving with Aldora. They have never had anything on board their boats blended below EAN 32 in my experience. Perhaps they might do a "custom blend", if asked.

 

[tursiops]

I am skeptical. Aldora is a first-rate operation that would not send its divers to 130 ft on 32%. I prefer to believe that rather than the OP's story. I also suspect he was not in deco, but was in the zone that is warning you about being close to deco.

 

[Lorenzoid]

Agreed. It was an adventure...Not for the typical cruise ship diver.

I dive with Aldora and am okay with advanced dives, just not that particular one. To each his own, of course.

 

[KenGordon]

My favorite dive operation on Cozumel (Aldora) routinely takes divers down into "Devil's Throat" using Nitrox 32. I recently dived this site and hit the first bar of deco on my computer. I would have preferred diving "Devil's Throat" using plain-old fashioned AIR, but in order to the keep everyone on the same profile...we had Nitrox.
Any opinions on this....?

As I recall that site involves 40m at some point. 5*32 is 1.6.

1.6 is a fine ppO2 at a stop, relaxed, on the way up and likely shallower than 40m.

At 40m on a nitrox mix, ie no helium, your gas density will be significant and tending towards reducing the effectiveness of your breathing and especially your ability to get rid of CO2. CO2 tends to exasperate the risk of an O2 hit.