Q about EAN and pony bottles?

[RDRINK25]

Lets take a scenario where I am diving with 32% for 25 min at a 100'. is it ok to breathe of my pony witch has air in it on my safety stop? Is this ok for any mix of EAN? Or should I always fill my ponys with the mix I am diving with?

 

[chrpai]

A safety stop is not a required deco stop so it's safe to breath air. That said, it shouldn't really be the plan though. You should have enough gas in your main tank to do the entire dive and the pony is only for redundancy.

You could also put 32% in the pony. Just make sure you never take it anywhere beyond the MOD for that mix. And if you do, and you end up switching to your pony, don't lollygag getting your butt back towards the surface. You would want to exceed the MOD for as little time as possible.

Dumping out the gas and filling the pony every time you switched mixes would be a waste...

 

[Mr Carcharodon]

If you are using your pony for emergencies it really does not matter what the mix is since you will not breathing it for a long time. And yes air on a 15 foot stop is fine since your EAD is not very different than standard nitrox mixes.

 

[elmer fudd]

The basic idea of the safety stop is to give your body a chance to metabolize the N2 bubbles in it. You can do that on air, but it's kind of missing the point. If your main tank is full of 32% then your safety stop will be more effective breathing that. You off gas quicker when you're breathing a lower percentage of nitrogen. If you're within your NDL however, then you can do your safety stop on air or any normal mixture of nitrox.

 

[NAM001]

personally i wouldnt be using the pony at all based on the dive's you describe. use the pony for an ooa event only.

 

[ianr33]

The basic idea of the safety stop is to give your body a chance to metabolize the N2 bubbles in it.

You metabolize N2?

 

[elmer fudd]

You metabolize N2?

Maybe a bad choice of words. Being a little tired right now and not an MD however, I'm not going to bother coming up with a better one.

 

[TONY CHANEY]

Using the pony properly, IMHO is not to increase your bottom time...that is staging, it is not to speed up your decompression time...that is advanced Nitrox / decompression. What it is designed for is to allow you to have a backup for getting your butt back to the surface should you have a gear failure / OOA situation. Picture it as a SpareAir on steroids. Now, with that said, you should have to use it almost never if you maintain your gear and watch your gauges but you really do need to practice using it. So keeping it full of air will be a better benifit to you because it will allow you to get on it fast at depths deeper that any Nitrox mix. You really don't want to fill and then dump based on everytime you switch back gas, question the MOD during a bad situation and heck air is cheaper than Nitrox. Remember, "I am diving with Al...he isn't good for much other than giving me gas." I hope that this helps.

 

[Landlocked123]

Totally agree with last reply. The pony should in no way be included into the Gas Plan for the dive and air won't introduce the risk of exceeding MOD on an Eanx mixture. Its all about the type of diving you do. The biggest risk factor I feel should contirbute to this decision is depth of dive and whether its a hard bottom dive or not. Last thing you can allow to happen is exceed your safe MOD in your backup gas (pony in this case) due to a down current and end up with catastrophic loss of primary gas at depth. That is when having Nitrox in the Pony could get you in trouble. Air would get you out of most such situstions. Given that you have not exceeded NDL at depths near the 100 foot range a 19 Cu/ft pony should be plenty to get to the top and even do a 3 min safety stop (not much more). Sure a 30 would be even better but a 19 is what I use and it will get me up safely.

 

[elmer fudd]

Totally agree with last reply. The pony should in no way be included into the Gas Plan for the dive and air won't introduce the risk of exceeding MOD on an Eanx mixture. Its all about the type of diving you do. The biggest risk factor I feel should contirbute to this decision is depth of dive and whether its a hard bottom dive or not. Last thing you can allow to happen is exceed your safe MOD in your backup gas (pony in this case) due to a down current and end up with catastrophic loss of primary gas at depth. That is when having Nitrox in the Pony could get you in trouble. Air would get you out of most such situstions. Given that you have not exceeded NDL at depths near the 100 foot range a 19 Cu/ft pony should be plenty to get to the top and even do a 3 min safety stop (not much more). Sure a 30 would be even better but a 19 is what I use and it will get me up safely.

Air should always be the gas of choice for a pony. The reason being, you can use it in an emergency from virtually any depth. If your pony were full of 50%, then it might kill you if you used it at 100'.

What I don't understand though is why someone would choose to do their safety stop on air if they've still got nitrox. Nitrox will make that safety stop just a little bit safer.

I can see where a diver might want to switch to their pony at the safety stop in order to practice doing it, but that didn't sound like what the OP was talking about.