Worth pursuing AOW?

[FinnMom]

It has been quite a number of posts since we heard from the OP (Aug. 20th last in this thread). I hope you are still out there.

20 Aug. you asked about the CMAS** class as an alternative to AOWD, esp. since you live in Denmark where many people are CMAS divers. My understanding is that CMAS in Denmark, like Norway, Sweden & Finland at least, is largely club-based. This would mean that the training might be cheaper or at least no more expensive than commercial options, but also include club membership. Club membership is likely to mean access to club boats, compressor, storage facilities, events, buddies, regularly sceduled local dives, etc. To my experience the clubs interest is in getting you trained, not turnover, so an need for extra dives, a one-on-one meeting to catch up on missed theory, flexible scedule etc. are not a business concern, just a question of when a qualified instructor has the time.

At least in my area, we require 50 dives experience before starting CMAS**. I think that is a good idea because having basic skills so much better in hand allows you to get more out of the training. I also enjoy not having ”yeah, but I’M a winderkind” -types in CMAS** classes earlier in their career, because that’s exactly an attitude we want to train away from - best not to indulge ”I can do things differently” attitudes by letting wunderkinds in with less experience than the mere mortals.

 

[Orestis82]

Hi, OP is here and following the thread with interest, but not much to contribute

I did join a local club and a club member was the one suggesting doing CMAS (she actually started over doing CMAS one star, even if she had OW).

I’ve done 10 dives already since I joined the club, most of them unfortunately in pretty shallow waters (max 5m), and a couple from a boat. Learned a ton, playing with my trim and buoyancy, also filled up some cylinders the other day - all great fun.

So I am continuing my education, if only by seeing what the experienced tech divers in the group do and going online and researching the heck out of it. The next thing in my list is actually to get and learn how to use a compass, and eventually deploy an SMB.

Regarding “official” training, I might do a drysuit course to be able to rent or borrow one for some colder dives. If some local instructor in the club offers a CMAS course, I’ll jump on it, but otherwise I might do a vacation AOW next summer in Greece

 

[AfterDark]

Hi, OP is here and following the thread with interest, but not much to contribute

I did join a local club and a club member was the one suggesting doing CMAS (she actually started over doing CMAS one star, even if she had OW).

I’ve done 10 dives already since I joined the club, most of them unfortunately in pretty shallow waters (max 5m), and a couple from a boat. Learned a ton, playing with my trim and buoyancy, also filled up some cylinders the other day - all great fun.

So I am continuing my education, if only by seeing what the experienced tech divers in the group do and going online and researching the heck out of it. The next thing in my list is actually to get and learn how to use a compass, and eventually deploy an SMB.

Regarding “official” training, I might do a drysuit course to be able to rent or borrow one for some colder dives. If some local instructor in the club offers a CMAS course, I’ll jump on it, but otherwise I might do a vacation AOW next summer in Greece

@Orestis82 sounds like you are doing fine. Learning trim and buoyancy in shallow is the way to go. The most noticeable changes take place in shallow water, if you can nail it 5msw then you'll be fine deeper. Do you use a compass for land nav? If not may I suggest you learn your compass on land then transfer it the water. In the water you may have to deal with current, drift even the way you kick may send you off course. There's a lot to UW nav learning how to use a compass is a small part. Use your diving compass on land, when you get in the water it will be familiar and one less thing to remember. We're very close to affordable UW GPS nav IMO you'll be enjoying it someday.

Sounds to me by the time you get to Greece you'll want an AOW card and not need training. In that case a vacation AOW course would be right. If you really wanted to learn something then if I where you I'd do something different, like the CMAS course, I can't remember ever hearing anything bad about CMAS. Vacation courses are what they are; a friend of mine went on vacation for 2 weeks with the family. His daughter took an OW at the resort. After a 3 day course the instructor handed her the OW card and told to her to come back tomorrow if she was interest in getting AWO. That doesn't sound good to me unless he is a SUPER instructor or she is a SUPER student, or both. Good move joining the club.

 

[yle]

Staying within NDL on air, nitrox or trimix is the surest way to avoid DCS. If a diver hits 500 psi 10 minutes before their NDL, lets say what good is nitrox going to do other than on multi-dives per day for several days? You can disagree all you like. It doesn't make what I posted untrue.

I would agree with you, provided that every diver knows exactly what their personal NDL is. Unfortunately most divers rely on general algorithms that are programmed into their dive computers. These algorithms are safe for the majority of people the majority of the time. But staying within the NDL displayed by a computer is no guarantee that a diver will avoid DCS. I guess I assumed you knew this... that a dive computer doesn't actually measure what is happening to that particular diver on that particular day on that particular dive.

You made the statement "If you can't exceed NDL with your tank on air then nitrox is a waste." This statement would be true if it was also true that staying within NDL is a guarantee that a diver will not experience DCS.

My mother is an active diver and is 70 years old. And she has more money than she can figure out how to spend. I have directed her (when it comes to diving she values my advice) to use nitrox whenever possible. Why? Considering her age and the extra $10 a tank, the cost compared to what she can afford makes even the tiniest benefit from using nitrox over air worth spending the money.

You might consider it a "waste" of the $10. But I would much rather she spend the $10 and have no benefit from it, than save the $10 and experience an "undeserved" DCS hit... leaving her with plenty of money but no way to go diving any more.

And this was the problem I had with your post: you were making a blanket statement that your experience should apply universally to everyone. New divers need to understand that everyone is different, everyone has a unique risk profile, everyone has a different definition of value (for some people, paying an extra $10 for nitrox is a lot of money.) It is useful to explain to new divers what works for you, but insisting that they agree with you and do exactly the same is short-sighted and ridiculous.

 

[AfterDark]

I would agree with you, provided that every diver knows exactly what their personal NDL is. Unfortunately most divers rely on general algorithms that are programmed into their dive computers. These algorithms are safe for the majority of people the majority of the time. But staying within the NDL displayed by a computer is no guarantee that a diver will avoid DCS. I guess I assumed you knew this... that a dive computer doesn't actually measure what is happening to that particular diver on that particular day on that particular dive.

You made the statement "If you can't exceed NDL with your tank on air then nitrox is a waste." This statement would be true if it was also true that staying within NDL is a guarantee that a diver will not experience DCS.

My mother is an active diver and is 70 years old. And she has more money than she can figure out how to spend. I have directed her (when it comes to diving she values my advice) to use nitrox whenever possible. Why? Considering her age and the extra $10 a tank, the cost compared to what she can afford makes even the tiniest benefit from using nitrox over air worth spending the money.

You might consider it a "waste" of the $10. But I would much rather she spend the $10 and have no benefit from it, than save the $10 and experience an "undeserved" DCS hit... leaving her with plenty of money but no way to go diving any more.

And this was the problem I had with your post: you were making a blanket statement that your experience should apply universally to everyone. New divers need to understand that everyone is different, everyone has a unique risk profile, everyone has a different definition of value (for some people, paying an extra $10 for nitrox is a lot of money.) It is useful to explain to new divers what works for you, but insisting that they agree with you and do exactly the same is short-sighted and ridiculous.

There are no guarantees when it come to diving and DCS in particular. Nowhere in my post that you read and quoted did I use the word guarantee. You made that up, for what reasons only you know. The standard NDLs for air are proven generally safe. That is not a guarantee. The fact is tens of millions of divers have dived for 150+ years counting hard hat on air within standard NDL safely without DSC. Old divers young divers nobody is going to die by not using nitrox, it is not unsafe to dive without it at any age. If you and mom feel better well that's what a lot of people claim, nitrox makes them feel better. At least you can put a finger on why it makes you and mom feel good, it makes both of you feel safe and that's a good feeing. I've found that an extra few minutes of SS after getting close to but staying within NDL makes up for any benefit claimed from nitrox, and I get to take a few more pictures.

No, I was not making any blanket statement that should apply to everyone another made up fantasy of yours.
I simply related my life long experience of diving with air to the OP. I didn't post the op must do the same in fact I suggested he find out if he can or can't benefit. And I then told him how anyone could benefit from nitrox. What the OP does or doesn't do about nitrox is not going to change my life one bit.

Please show me the hard science that supports the claim of reduced DCS among divers using nitrox of any age group. I am unable to find it on my own.
Not studies that suggest or indicate or other speculative double talk, hard facts please.

After you can't find any answers, you really should get this making up things you do checked by a professional.

 

[AfterDark]

@doctormike says it better than I.

DCI and the perils of diving in a mixed EAN/Air Group

"Nitrox doesn't make you less likely to get bent unless you are gas limited. If you are doing dives where you are ascending when your NDL gets close to zero, nitrox will give you a longer dive, but your decompression stress and tissue loading will be the same. If you want to build in a DCS buffer, then you need to load less inert gas or extend your decompression profile."

 

[DeepSeaExplorer]

At most depths, divers can’t even near the NDL on a single tank with Nitrox. So, it naturally reduces the chances of getting hit pushing NDLs.

Nitrox really makes the difference on repetitive days, over multiple days. In those circumstances, it allows a lot more accumulated bottom time and reduced N2 loading.

 

[Foothills]

@DeepSeaExplorer, I agree with your second point, but wonder if your first paragraph is entirely correct given the increasing availability of 100 cf rental cylinders and the number of recreational side-mount divers I see.

Most divers I know can get 60+ minutes at 60' on a 100cf cylinder in warm water (an RMV around 0.6 cfm). IIRC thati is the NDL on the US Navy table (my memory is shaky, so I could well be wrong).

 

[AfterDark]

@DeepSeaExplorer, I agree with your second point, but wonder if your first paragraph is entirely correct given the increasing availability of 100 cf rental cylinders and the number of recreational side-mount divers I see.

Most divers I know can get 60+ minutes at 60' on a 100cf cylinder in warm water (an RMV around 0.6 cfm). IIRC thati is the NDL on the US Navy table (my memory is shaky, so I could well be wrong).

https://www.dir.ca.gov/oshsb/decompressionAC-USNdivetables.pdf
Page 8 of 25

The USN tables show you are correct 60FSW 60min NDL. The table shows the same NDL for enriched air, if I'm reading it correctly AIR/O2 = nitrox. After that is appears to me the difference is in the stop time, the rep group remains the same regardless of air or nitrox. Without looking at the notes I'd guess the O2% would be the max for the given depth.

 

[wetb4igetinthewater]

So I am continuing my education, if only by seeing what the experienced tech divers in the group do and going online and researching the heck out of it. The next thing in my list is actually to get and learn how to use a compass, and eventually deploy an SMB.

Wait, you didn't learn this in your open water course?

I might do a vacation AOW next summer in Greece

Please post if you decide on this and are looking for a recommendation. There are some good places. And there are places that violate standards (example: open water certs given to people who only completed confined water dives).