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View Full Version : Doing my Nitrox cert through ANDI



freediver
11-16-2007, 02:47 PM
I'm in the process of completing my ANDI Nitrox cert and have some questions I hope can be answered.
Is it advisable to get a personal O2 analyzer to verify fills?
I have a Poseidon Cyklon reg and ODIN octo with Poseidon analog console and both Cressi Arcimede Nitrox ready dive computer and my Suunto D3 which also does Nitrox as a backup - How would I find out if my regs are Nitrox ready? My local LDS isn't a Poseidon dealer.
I'm looking to get my first personal tank - I want to find the balance between lightweight and max dive time. Being a freediver, I love the idea of a low profile (double 40's seem ideal to me) - any recommendations?

bottlefish
11-16-2007, 05:17 PM
1: You should be checking your nitrox fills directly before the dive as well as when you leave the dive centre, just in case a cylinder has got muddled on the way. It shouldn't happen if the marking has been done correctly, but why take the chance. O2 analysers are cheap, so yep, I would recommend buying one.

2: First of all, do you need Nitrox ready regs? UK standards state you have to have O2 clean regs if the O2 content is over 40%, anything below this, standard regs are fine, I don't know what the US standards are though.

Nitrox ready regs are sold/supplied as nitrox ready/O2 safe from the manufacturer (in the UK atleast). The first stage and second stage are green, as is the hose sometimes. If you've just bought standard regs, then chances are they aren't O2 safe, if you've used them with ordinary air, even more so. Getting an O2 clean on a reg set is also relatively cheap and easy, so if you're not sure, throw them in anyway.

3. Sorry, can't help there! I dive single 12 litre for recreational and double 12 litre for tech, no experience with anything else.

BamaCaveDiver
11-16-2007, 07:25 PM
1. I would say most definitely if you are diving on a frequent basis. Sensors are expensive, and despite a few tricks for prolonging their life, once the membrane has been exposed the clock is ticking down. If you are not analyzing your own gas, be sure to carefully watch whomever does it for you at your LDS to ensure a proper reading, and even then I would opt for a much lower PPO2 to avoid the effects that errors can have underwater (read, not everyone in a dive shop knows everything about what they are doing, and consumables like oxygen sensors often get pushed to the max before being replaced.)

2. Never pass 100% oxygen through any piece of equipment that you have not personally verified to be compatible for oxygen service. However, unless you are breathing high O2 mixtures, your regs should be fine. The real problem comes from high concentrations of O2, such as you would see hit the valve and cylinder doing partial pressure fills (the regulator is not being utilized during this process, so the only thing that matters there is the final percentage of your mix.) Personally, I would most likely rebuild the regs (if I had not done the last rebuild myself) to ensure that they were clean, free of hydrocarbons (silicon based lubricants), and utilitized EPDM or Viton orings, but then that is just the way I like things (there are several divers diving such rigs without employing these extra precautions.) It is certainly something to keep in mind the next time your regs need to be serviced though.

3. Find the cylinder setup that fits your style of diving, just keep in mind the various trade-offs that were mentioned in the other threads.

Please note that this is my personal opinion; I am not a professional and have no desire to be. I am just a diver who is continuously learning and having fun.

Something else to keep in mind is that we seem to be seeing more folks who are somewhat susceptible to elevated PPO2's. For year's it was thought safe to use 1.6 at rest (deco) and 1.4 during the working portion, but a couple of folks diving these numbers have not been so fortunate lately. Go slow and have fun.

freediver
11-16-2007, 11:16 PM
Bama, can you elaborate on the elevated PPO2's issue in your last paragraph?

The course work from ANDI I'm reading seems to indicate otherwise.

I'm looking at using EANX and diving regular air profiles so that I would have that extra safety margin when blowing bubbles.

Any thoughts on this?

bottlefish
11-17-2007, 09:28 AM
Bama, I'm still using a 1.6 max on deco stops, your post is news to me too.. I'd be grateful for any further info you may have

amtrosie
11-17-2007, 03:25 PM
I would echo what Bama said. Because I deal more with the regulator servicing side, I would be stronger in my admonition that elevated O2 mixes should only used with properly cleaned regs. The exact point where the petroleum based O-rings and lubricant become combustible will vary with ambient temp., atmospheric press.(all be it slightly), etc. I have heard from many sources that anything below 30% O2 is safe. My personal feeling on this is that ANY ELEVATED Oxygen breathing mix should have properly cleaned regs. This is overly cautious, I admit, but I have been the witness of carelessness around Oxygen, so have adopted this cautious mantra.


The tanks: go with what suits your style. The expense of doubling up 40's seems excessive for the pay-off, but you alone know this. I would encourage you however to dive several set-ups to be sure. An option my be to double up some old steel 72's..... just a thought.

As for the last point, I'll let Bama chime in, although I know what he is referring to. I personally dive a ppO2 of 1.2 ATA (working), and use 1.6 ATA ppO2 for deco. I think there is something to be said for the deep stops. (This is not applicable in two of the latest accidents) The important thing to consider here is 1. Start Slow!!!! there is no rush. Let your body get acquainted with these mixes, under pressure. Learn how YOU respond to different scenarios! 2. The Internet is NOT the place to learn how to deal with this! Go to individuals well acquainted with different gas mixes and LISTEN to them. 3. We each respond differently, even on different days, so PROCEDE WITH CAUTION AND LISTEN TO YOUR BODY!!!! 4. DO NOT UNDERESTIMATE the value of physical fitness. For you personally, this may not be so much an issue, but for many others it is a major issue.


I hope this helps.

acelockco
11-17-2007, 05:03 PM
I really think all of your questions will be answered in your class, and ANDI book/DVD or whatever else you get from your class. Just ask questions in class and you will learn what you need to know.

The only question that will not get answered is your double 40's question.

Again back to the other post....stick with the single cylinder. You are going to add so much weight for the same amount of air/gas. I am thinking after you actually get some dives in, you will understand. If you are really going to go with doubles (and I think you shouldn't right away), then you will most likely want at least double 85's steel. There has to be a decent payoff for all of the extra weight.

I guess if you really want to be streamlined, you can take like 6 14cubic foot pony bottles and make a rig that wraps them around your belt area. You will be the laughing stock of the scuba world, but you will have your freedive feeling and still get a bit more than your 80 cubic feet. Just messing around with that idea, DON'T take it seriously.

Remember, you are not required to reinvent the way we dive in order to enjoy scuba.

BigBlueTech
03-01-2009, 09:16 AM
I'm in the process of completing my ANDI Nitrox cert and have some questions I hope can be answered.
Is it advisable to get a personal O2 analyzer to verify fills?
I have a Poseidon Cyklon reg and ODIN octo with Poseidon analog console and both Cressi Arcimede Nitrox ready dive computer and my Suunto D3 which also does Nitrox as a backup - How would I find out if my regs are Nitrox ready? My local LDS isn't a Poseidon dealer.
I'm looking to get my first personal tank - I want to find the balance between lightweight and max dive time. Being a freediver, I love the idea of a low profile (double 40's seem ideal to me) - any recommendations?

My 2 cents

1. Any time you get nitrox filled, they will have an analyzer. Any time you pick up a pre fill, they will have an analyzer. If they don't then don't use them. It's like suggesting your should bring a dive mask for your instructor. The company i work for is a technical diving school and the costs for analyzers alone for helium, co2, o2, ccr is very expensive, not something you would really need to get into for recreational diving.

2. Typically, if you're regulator has been serviced since 2000 it is compatable up to 40% nitrox. It was only the old rubber or new style silicon O-Rings that reacted badly with higher concentrations of oxygen causing perhaps the piston to stick or leaks. If your manufacture says it's ok then it's ok. As for the computer, i suppose a back up is nice, however you should be doing no decompression dives anyway, so if your computer fails you end the dive.

3. Double 40's is ok, if you're going to be using nitrox in it, find out what blending method your local filling station uses. If it's continous flow you're fine to go from air to nitrox up to 40%. If it's partial pressure you need to get it oxygen serviced and retain that service rating.

BigBlueTech
03-01-2009, 09:23 AM
Something else to keep in mind is that we seem to be seeing more folks who are somewhat susceptible to elevated PPO2's. For year's it was thought safe to use 1.6 at rest (deco) and 1.4 during the working portion, but a couple of folks diving these numbers have not been so fortunate lately. Go slow and have fun.

I think you might be quoting a very unusual situation. In my experiences and my colleagues experiences both in military diving and commercial diving with hyperbaric services - The majority of people have a reaction at 3.2 - even in chamber treatments you're comfortably breathing pure oxygen at 18m (2.8 ppo2) However there are always CNS exciters like cold for example that can cause vascular constriction. In my professional opinion, many "Nitrox" divers experience narcosis before cns toxicty and relate it to the nitrox rather then the nitrogen.

The 1.4 - 1.6 rule is extremely conservative. My time in commercial diving had me breathing pure oxygen at 9m (1.9) - albeit in a hard hat but i've never heard of a cns hit from that or recreational nitrox - people switching to wrong gas at depth or ccr now that's a different story. I will agree that like anything slowly is best but i have agree that people should not be warned about nitrox as it's clearly commercialy viable for the recreational diving industry. After all.. padi hopped on the wagon in 1995 and since then it's been everywhere.