Decompression Tables for Nitrox

[Aquabot]

Can I ask a question - I think I understand your point about ascending slowly enough to the surface to avoid any "stop or stops"... It makes sense if you had enough gas and could control the ascent with precision - which is currently beyond my buoyancy control.
But does it "really" matter the ascent rate to the first stop? Taking the shaken Tonic Bottle approach (yes I am originally from Boston and can't say Pop or Soda) - will I cause bubbles to form if I ascend faster than 30 feet per minute to my first stop? Or is that overblown theory and as long as you hit your stop and stay there you are relatively safe?
Thanks.

Originally it was taught to ascend no faster than 60 fpm. Some may still teach that but generally it isnt.

To answer your question, yes your ascent rate matters. Decompression tho is still a theory tested on every dive and nothing can guarantee that you will not develop enough "bubbles" to become bent. People do get DCS even while following NDL.

A slow ascent is prudent because it allows you to control your ascent so that you do not "miss" or blow past stop. Which depending on your depth and time at depth could prove fatal.

May I ask, why such a interest in decompression if you are aware that you don't posses the skill level to safely conduct those type of dives?

 

[Basking Ridge Diver]

No, the 60 would be fine (if you are not too close to the surface), but you'd only spend half as much time getting to that next stop, so you'd only get half as much off-gassing during that ascent. When you set up the software, it asks what ascent rates you will use. That is so it knows how long you will be getting some off-gassing between stops. The point is the fractional releaase of pressure...so a 10 ft ascent when you at 100 ft is a small fractional release (10/133), but from 30 ft to 20 ft that change is a much larger fraction (10/63) of the ambient pressure. So going faster deep is ok, but you want to go slower when shallow. Also, there is the problem of trying to offgas when you are very deep.....you may be releasing pressure, by ascending, but some of your "compartments" may still be on-gassing. This is sometimes approximated by some cross-over depth (probably around 80 feet in the OP's 120ft-max example), below which you are still on-gassing, and above which you are usefully off-gassing.

So If I understand - going 60 feet per min and not 30 feet per min would cause me to accrue a bit more deco when I hit my first stop than if I was slowly ascending less than 30 feet per min?

 

[tursiops]

So If I understand - going 60 feet per min and not 30 feet per min would cause me to accrue a bit more deco when I hit my first stop than if I was slowly ascending less than 30 feet per min?

More exactly, going 60 instead of 30 (used to plan the dive) would mean you have not off-gassed quite as much during your ascent, so your mandatory stops would be a bit longer to make up for that, except you win a bit if you ascend 60 from down deep because you are doing less on-gassing at depth.

Best is to ascend at 60 when you are deep, maybe 30 or less during your deco stops, and 20 or less near the surface.

Please note the 60 fpm is not just plucked out of the air....there is a long history of how it came to be, how safe it is, and when you should go much slower than that.

 

[Remy B.]

have someone by any change taken both TDI and Padi nitrox course that can recommend which one have more rich material, I know the instructor make the difference, but material vise one book have more to offer over the other ?, is TDI that same as Padi, not even Half a day of class room and 1 tank, I already know the recreational part of Nitrox use, but I' kind of a rat book.

I actually will take the Nitrox plus 2 tanks maybe a 3rd tank if Instructor allows, just for the extra time in the water and to go back quicker in the water since the day will be short.

 

[tursiops]

The classes are almost identical. The PADI books are better. Neither recreational class covers any of the stuff you've been questioning in this thread, other than how much NDL do I get?

Be patient, take the class, then move to technical nitrox and begin to get your questions answered.

By the way, neither the PADI nor the SDI class has any required dives.

 

[Edward3c]

have someone by any change taken both TDI and Padi nitrox course that can recommend which one have more rich material, I know the instructor make the difference, but material vise one book have more to offer over the other ?, is TDI that same as Padi, not even Half a day of class room and 1 tank, I already know the recreational part of Nitrox use, but I' kind of a rat book.

I actually will take the Nitrox plus 2 tanks maybe a 3rd tank if Instructor allows, just for the extra time in the water and to go back quicker in the water since the day will be short.

There's nothing special about Nitrox, we (BSAC) have it built into our core training at both Ocean Diver and Sports Diver. Like all diving: "Plan the Dive, Dive the Plan".

 

[Remy B.]

I know there is not a lot special to learn on the Nitrox course, I believe I know what needs to be known for recreational nitrox, except for deco times with Nitrox, here in the Island they offer you a free tank with the course, some other places two free tanks ( that is the one I will take ), I will see if I can purchase a 3rd tank and have the instructor or DM come along.

 

[Basking Ridge Diver]

May I ask, why such a interest in decompression if you are aware that you don't posses the skill level to safely conduct those type of dives?

Sure - I am playing with Excel just because I am not diving now. So I built an excel worksheet using Naui Tables and Navy Tables that allows me to enter 3 dives (Depth in 10 foot increments (40 to 130 ft for Naui and 190 ft for Navy), Time (Minutes only) and on the 2nd and 3rd Dives SIT (Minutes)). It kept me busy - it does both NDL (In Green with Ending Letters for each dive) and Decompression times (in Red with Ending Letters and Deco Time). Any way it started out as a challenge to see if I could do it - it works and now I am thinking of enhancing it.

I am OW and Solo Certified - I may get AOW this spring because my son is now diving with me. But I was never interested in Nitrox or Deco diving - now it is just a mental exercise and the more I learn the more I realize how complex this can be to plan. I don't see myself going beyond this point but it is fun to explore and think about the options as well as reading the threads in various forums it allows me to understand the concepts and points being made.

So I appreciate the small amounts of knowledge being shared - but at this point I don't have the wallet or the dedication to pursue it beyond the theoretical point.

 

[HIGHwing]

All good fun, but don't dive an Excel table you made yourself, obviously.

 

[chrisch]

All good fun, but don't dive an Excel table you made yourself, obviously.

True. The PC will not work underwater