TDI CC Rebreather (Air Diluent) - Advanced Nitrox

[Scuba-Lad]

Hello,

I searched online for the answer to this question but couldn't spot anything so thought I'd ask on here.

Does anyone know, if you complete the TDI CC Rebreather (Air Diluent) non-deco, since the rebreather is injecting pure oxygen into the loop, does this mean you also earn the Advanced Nitrox cert at the same time? I'm aware that if you don't already hold ANDP then the course doesn't cover you for doing deco dives on the rebreather, but I was curious about the advanced nitrox part since we are using bottles of 99% O2 on the rebreather unit. I know that there's a TDI path to progress to deco after a certain amount of hours on the unit, but my question specifically relates to if I passed the initial rebreather course, could I then take tanks of Nitrox up to 100% in order to off-gas faster on my OC dives (but no deco of course), since I don't currently hold AN cert

SL

 

[inquis]

I can't speak to the AN cert, but the perceived benefits of your scenario don't actually materialize:

could I then take tanks of Nitrox up to 100% in order to off-gas faster on my OC dives (but no deco of course)

Breathing O2 instead of air on a 5 minute safety stop after a 60 ft NDL dive (GF x/85) gives you a single additional minute of NDL and obviously less for other nitrox mixes. (I also assumed a 1 hour SI.) IMHO, O2 has no place on OC dives until you are doing deco.

 

[OTF]

Don't do dives with gas switches without training to do gas switches.

 

[formernuke]

Same as above, if your not going into deco what's the point of switching to OC.

If I do go into deco on my unit I don't switch to OC, just do a o2 flush at 20 feet.

 

[broncobowsher]

Not knowing your local dive shop scene, they may not fill 100% without an AN cert.

Ask your instructor if you get an AN cert with the rebreather class. It is likely to just make the rebreather class longer and more difficult as you have to learn about the AN stuff to anyway if you don't start with it.

What I am familiar with is the AN class is a pre-requisite for the rebreather. May not be in the TDI structure, but the instructor will make it be. Or it could be worked into the class.

If you are not doing deco diving (mandatory decompression stops) there is really nothing to off-gas faster to get out of the water. You are free to leave at any time. Even the safety stop isn't mandatory, it's just a good idea.

So you want to use 99% O2 without proper training, but think different training will cover you. That is an "ask your instructor" question. The short answer, no. You don't know what you are doing. That is what there is training for. Long answer, as pointed out above, you are probably going to have to get that AN cert as part of getting the rebreather class.

 

[Marie13]

I did the TDI Air Dil (no-deco) CCR class last year. You do NOT also get Adv Nitrox.

 

[formernuke]

I did the TDI Air Dil (no-deco) CCR class last year. You do NOT also get Adv Nitrox.

They didn't make you take it with the course? For mine (IANTD) AN was a prerequisite or had to taken with it. But I was also doing a deco version of mod1

 

[formernuke]

OP to elaborate why using a rich bailout if not going into deco is pointless.

Let's say 100 foot dive OC using EAN 35. Your ppo2 at 100 is 1.4. As you come up, say to higher level of wreck etc your ppo2 is no longer 1.4 so your off gassing in not as efficient as if it was still 1.4.

At 67 feet your ppo2 is now 1.05, 44 feet it's now .7 etc.

With the rebreather you are maintaining your ppo2 at 1.3 the entire dive including your ascent. I was taught to o2 flush at 20 feet which increases my ppo2, but I was doing a deco ccr class, that being said even if keep 1.3 your only .3 away from 1.6 and on a non deco dive your not saving any real time at all.

Adding extra bailout complicates the dive, don't do it unless necessary.

 

[Marie13]

They didn't make you take it with the course? For mine (IANTD) AN was a prerequisite or had to taken with it. But I was also doing a deco version of mod1

My instructor does not require *any* OC tech certs at all before doing the basic CCR class - air dil, no deco, 100’ max. Call it recreational CCR, if you like, instead of Mod 1.

So no, I didn’t do AN.

 

[Marie13]

OP to elaborate why using a rich bailout if not going into deco is pointless.

Let's say 100 foot dive OC using EAN 35. Your ppo2 at 100 is 1.4. As you come up, say to higher level of wreck etc your ppo2 is no longer 1.4 so your off gassing in not as efficient as if it was still 1.4.

At 67 feet your ppo2 is now 1.05, 44 feet it's now .7 etc.

With the rebreather you are maintaining your ppo2 at 1.3 the entire dive including your ascent. I was taught to o2 flush at 20 feet which increases my ppo2, but I was doing a deco ccr class, that being said even if keep 1.3 your only .3 away from 1.6 and on a non deco dive your not saving any real time at all.

Adding extra bailout complicates the dive, don't do it unless necessary.

He indicated he wanted to take 100% on OC dives, without being trained on it for OC use.