YD Scuba Diving Forums banner

Deep air.......

13K views 60 replies 24 participants last post by  nigelH 
#1 ·
Hi guys,

I realise I may be opening a bag of worms here so you have my apologies in advance!

I'm relatively new to diving, I got my OW about 18 months ago and worked my way up to rescue diver level. I've done about 60 dives + pool time practising skills etc with a club. I've also been to tekcamp to get a feel for what Tec diving is about and whether it would be for me or not, as it turns out I loved the experience and am looking to progress this new found passion even more.

I thought I would join my local BSAC club as they offer discounted technical training to there members, and this is really where my problem starts.... I was talking with there resident advanced diver/tec diver and he was telling me that to qualify for the Sport diver qualification I have to do a deep dive going into deco on air...

All be it I'm not greatly experienced I have read Deco for divers, and am quite happy that my understanding is that deep air is a bad thing is correct. Also lectures and conversations I've had a TekCamp have reinforced that opinion.

As a result I refused to do the deep dive on air but said I would do it on a more appropriate gas that had a reduced risk of narcosis. The advanced diver couldn't understand my rationale. So my question is.... Have I missed something?? Is deep air actually safe?? Or have I simply encountered someone who is 'old skool'?

Cheers for your input
 
See less See more
#4 ·
He's wrong, but as he cant defend himself maybe it could do with some more clarification
before we get the flaming pitchforks out.

First off the award of Sport Diver is not conditional on doing deeper dives. The maximum
depth on the course itself is 20m and once completed there is a mandatory requirement
that you should be signed up as a Sport Diver.

After that if you want, you do progression, 25m, 30m, 35m. None of this is compulsory,
but if the club is doing a 30m dive and you've only done 20m, it's unlikely that you'll be
on the boat. Is this what he means and you've confused it with the grade itself?

That 35m max depth for Sport Diver is not 35m+ it's an absolute, so usually it will be
approaching, which would be about 33m odd.

At that depth 32% backgas would be ideal and naturally preferable to air.

To me your post throws up more questions then answers and maybe you need to go back
and ask a few more questions.


If it was me and I was your Instructor, i'd start to introduce Nitrox in progression and
wouldn't rush to 35m, building up over a few dives and before hitting 30 introducing
redundancy, before finally doing the max on 32%.

I have done the same on air, but that was when better gases weren't around and as Sport
is a Nitrox grade, don't see the point in not using the opportunity to teach good practice at
the same time.
 
#5 ·
I certainly don't want to bad mouth anyone, hence why I've been a little vague.

I've done dives to the limit of my current certification and am comfortable in the 25 - 30m range. Since getting my Nitrox card I always dive on nitrox (32% most of the time), and I'm comfortable diving my 12L twinset with wing. He was quite clear in saying that the deep air dive at 35m with deco was part of the sport diver program. I later confirmed this with my wife as she joined with me, at the same level. I did wonder if I'd misunderstood what he had said to, but she understood it the same way.

I've only joined the BSAC club in the past couple of weeks so have only just recieved the Sports Diver pack. It was because I couldn't see anything about it being a mandatory part of the course, and because of the course appearing to be nitrox focused (as far as breathing gasses go) that I decided to post the question.

As I said, I'm not out to give anyone a bad name, but I did want to get third party opinion in case I've misunderstood the theory of breathing gases and saturation.
 
#7 ·
He was quite clear in saying that the deep air dive at 35m with deco was part of the sport diver program.
I don't want to sound critical but 35m is not "deep" air.

Typically we would only call a dive "Deep air" when its in the 40-60mtr range IMO, also under BSAC guidelines you are perfectly within the rules to dive air to 50mtrs. You will also meet lots of divers who've done 60m or more on air, especially on holiday (not saying its right or wrong, good or bad but it is a fact)

Sounds like you might need to clarify a few things with your club, perhaps they are talking about DL training? If you have your training pack you'll see all the dives and requirements explained within- including the depth limits/requirements.

You should only do dives you feel happy with but also consider whether the instructos had any agenda to sell you further training when they where downplaying air diving beyond 30mtrs ;-)

Lastly- It sounds like you haven't dived to 35mtr on air? Its unusual to have bad symptoms of Narcosis at that depth, beyond 35, yes most people feel it but not above. Don't rush to gain more qualifications- there is no substitute to lots of diving in mixed conditions in your logbook, depth can wait- be a good diver first :)
 
#6 ·
Hmm, like you I don't want to step on toes, but this doesn't sound right at all.

According to SALT, you cross-over as a Sport Diver, so you should actually be on Dive Leader.
www.bsac.com/core/core_picker/download.asp?id=10131

I have in the past advised the odd divers with Rescue to do Sport anyway, but that was because
they had no Nitrox, Deco, Drysuit and UK techniques DSMB etc. and it was better just to do a
fastrack Sports to ensure we covered the lot, but that was with the students agreement.

This doesn't appear to be the same in your case, in fact twinned up already using Nx, would be
better than a lot of standard (non-crossover) Sport divers. Even that depth is a bit wooly, if
you dived upto 30m, then anything over = 35m, dont have to go to the max. I wouldn't put on
a special dive for that, we'd just do it on a normal one.

My advice is to print off the SALT leaflet, show him and ask why you are doing Sport Diver when
according to the table you already are.






.
 
#8 ·
Out of interest, why do you physically need to go into deco? You could plan a 35m deco dive, work out the deco schedule but say only go to 30m or only do a limited amount of time. However you will still do all the planned decompression on the way up.

That way you've proved you can plan & proved you can follow a decompression schedule


TG

Sent from my iPhone using Timmytalk (hopefully)
 
#9 ·
He shouldn't have to, which is why I think there maybe a bit of misunderstanding going on here.

IM says

Depth Experience
Newly qualified Sports Divers, wishing to increase
their depth experience, should be encouraged to do
so in a progressive manner, in increments of
approximately 5m. They should be accompanied on
such dives by a diver holding a minimum
qualification of Dive Leader, and all such dives
should be performed under the supervision of a
NQI.







.
 
#10 ·
Thanks for all the input guys, it's greatly appreciated.

While I appreciate you can dive to 50 meters on air, why would you want to if there is a safer alternative available? If it's 'because you can' or 'I'm on holiday' I'd start thinking that you possibly haven't thought of the possible risk that you're exposing yourself and your buddy to. Especially as there are safer ways of diving to that depth. That being said, each to their own, it's that individuals risk to assess and make a decision about.

You're right in thinking that I haven't dived to 35 meters on air, to be honest I don't think I've been past 18 on air. I got my enriched air card quite soon after I qualified and have been diving nitrox since. Within the limits of each gas mix it's a safer alternative to air so thats what I choose to dive as a result.

I'm not concerned with going deep at this point in my diving, or even with going into deco. My question was really about whether I had misunderstood what the advanced diver had told me or had I misunderstood the gas theory etc.?
 
#13 ·
While I appreciate you can dive to 50 meters on air, why would you want to if there is a safer alternative available?
"Safer" is a really Dangerous term :)

If you do the math you might find other gases, even air or a combination are "safer" in terms of decompression, narcosis isn't always the primary concern.... but don't worry about that, its not important now, crack SD first!

If it's 'because you can' or 'I'm on holiday' I'd start thinking that you possibly haven't thought of the possible risk that you're exposing yourself and your buddy to. Especially as there are safer ways of diving to that depth.
You will hear it, Sadly a percentage will be for silly reasons as you state... another reason is Air is often the only available gas! Even in the UK some shops/air stations can't do Nitrox and Trimix. Don't discount Air totally, on a relaxed dive espeacially you can have long deeps dives on the "wrong" gas very safely- this may come up if you are stuck in a fixed location (like on Holiday) its not "dangerous."

There are always "safer" (theres that dangerous word again) ways to do things- a submarine in this case :) Nitrox is not perfect afterall, I'm sure you're well aware of its limitations- for example, depending on the mixture it becomes toxic and dangerous much shallower than air, a great pain if you gas up for a dive and then the site is changed!
 
#11 ·
Terry's responses have been spot on.

What I think you're instructor meant to say was that as part of the SD syllabus there is a simulated deco dive. In this one I usually get my students to plan a 35m dive with deco and we actually do this dive plan but go no deeper than 20m.

Just out of interest - where in Suffolk are you? I have contacts in that area who may be able to help you out...

Regards

Steve
 
#12 ·
Agree with what has already been posted. You have to do a 'simulated decompression dive' as part of the course - there is no minimum depth for this, so could easily be a 20m dive using nitrox but planned on air.

Depth progressions are optional, after certification, and have no prescription as to which gas you should/should not use, other than the normal BSAC rules around gases you are qualified to use etc.

Definitively stating that you must dive to 35m on air is. Of a BSAC requirement. It's probably a misunderstanding rather than a case of enforcing 'additional' requirements, but you can see from your QRB and sports diver pack what the requirements are, and shouldn't be forced to do a dive you're not required to do in order to have your qualification signed off.


Sent from my iPad using Tapatalk HD
 
#16 · (Edited)
Dive the way you want to dive - if you don't like what your instructor is saying, go outside and kick the first tree you come across. Half a dozen PADI instructors will fall out of it and will gladly take you (and your money) on. If you want to go tec then do a recreational trimix course. That way you can deal with the narcosis (if that is your concern) and dive safe. Don't be too timid with the depth thing - you will need to do this at some stage, but you are right to go at a comfortable pace for you; confidence is the key to safe diving.

Deep air used to be standard; it comes with risks but it isn't complete madness as mentioned above. I find things just take me longer, that's all. A task which took me 2.5 minutes on the surface took me 5 minutes at 55m (OC). Clear head, just had to concentrate harder. On closed circuit on air (on holiday!), 78m with a real tingle (O2 isn't the main issue here, pN is!). This is peanuts though; in the old days, people would do 100m+ OC. Some of them may even still be alive. :)

Other than the odd blip, I dive every dive with He in the mix. Having a clear head is very sensible. If I were you, I would be testing myself on the air but getting into trimix asap (recreational depths) - IF you can afford it. (And assuming you really DO want to go Tec)

Have fun! :)
 
#17 ·
I'm with Ben all the way on this one, 35m is not a 'deep air' dive. I am constantly amazed at what some of the internet experts consider unsafe. Sometimes air may not be ideal but it's 'safe' to breathe down to about 60m (depending on what ppO2 is in vogue this week). Deeper than that you are gambling, many have gambled and won and some have gambled and lost. At deeper depths beyond about 30m ish it is the individuals susceptibility to Nitrogen Narcosis that becomes the limiting factor. However when it comes to nitrogen narcosis susceptibility everyone is different, personally I notice the onset of narcosis on OC air between 40 and 45m (and by 70m I'm definitely smashed), on CC air I notice the onset at around 35m (which is why I use trimix past 40m on CCR), others may feel it earlier or later.

I'm actually of the opinion that a 35m air dive is a sensible thing for the club to encourage you to do as how can you judge where your own limits are if you've never been to the edge of them? to steal and paraphrase a sentence from Dave Sutton on another forum 'experience is only gained when operating at or just past your comfort zone'. Build up your air diving depth experience in a series of dives of say 20m, 25m, 30m and then 35m. I would be amazed if you notice any difference to diving nitrox.

Is it not reasonable for a club to expect any sports diver or dive leader to be able to conduct a 35m deco dive on air before being let loose on their own or taking responsibility for someone else? When I was a DO I certainly would never have awarded a DL qualification to someone who was uncomfortable with doing that dive. As has been said earlier nitrox may not always be available, what are you going to do when there is no available nitrox? limit yourself to 18m?

Remember diving isn't like skydiving, you're not committed once you jump off the boat, if for any reason you feel uneasy at any point during a dive you can call it and head back up to where you are more comfortable.
 
#18 · (Edited)
I will freely admit I don't notice any impairment diving deep (45m+) air. I felt totally on the ball, just a bit 'mellowed'.

However once I started diving a rebreather full of trimix I couldn't help but notice how much divers on air or nitrox slowed down when presented with anything slightly out the ordinary so, guessing that I was the same, I will no longer dive below 30m without some helium in the mix.
That however is a personal choice and I carry the costs.
 
#19 ·
I dived the sanfrancisco maru at 55m on air in clear warm blue water and had a clear head and felt comfortable I have done 30m sea dives in 2m vis with all the feelings of narcosis. Was it in the mind and just fear? Was it narcosis? Who knows? Narc is a state of mind mixed up with the effects of narcotic gases. Its not all about depth imo
 
#20 ·
Thanks again for all the new contributions to the thread. It's interesting to see how opinions differ, and also how different circumstances around the world may dictate how you dive to an extent.

I think NigelH's post raises something I tried to highlight, that although you may feel fine you could actually be impaired. And when faced with a task or a situation to deal with you may not be able to respond as quickly as you could have with a clear head.

Someone earlier in the thread mentioned that they did a test in which a task took 2.5 minutes on the surface and 5 minutes at depth on air. What if that was a time critical task i.e. a gas shutdown - there is a real possibility that your tank would be empty before you completed the procedure.

Someone else mentioned diving to your limit or just beyond it, so you know where they are. That's a principle I follow to a point, but when the potential consequence is unconsciousness and drowning?? I don't think so.

I personally think that if there is a safer way of doing something, we owe it to ourselves, our buddies and our families to make sure we do all we can to ensure our safety.

I don't mean that to sound like a cheap shot at anyone as we all have different experiences that fuel our opinions. As someone who is quite new to the diving world I value all your input and opinions, so thank you to everyone that has contributed.

Sent from my iPad using Tapatalk HD
 
#22 ·
I don't mean that to sound like a cheap shot at anyone as we all have different experiences that fuel our opinions. As someone who is quite new to the diving world I value all your input and opinions, so thank you to everyone that has contributed.

Sent from my iPad using Tapatalk HD
Don't worry. All the people that would have shot you down for that don't post here anymore :D

For me- diving is about comfort and being able to trust yourself. You increase your boundaries by being a little more adventurous each time, but within your capabilities and the limitations of your life support equipment (as that is what it is)

The big thing is not to get complacent - which happens with a few years experience. That is when you are most at risk.

I see people sneer at so called newbies, but in reality, alot of diving accidents are the experienced guys pushing the limits too far. We are all fallible
 
#21 ·
TBH unconsciousness and drowning is something I am more concerned about when diving devil gas that may have too much or too little O2 in it for the depth I'm at. Air is the one gas there is that you can breathe OC without worrying about passing out or fitting at all 'normal' recreational diving depths. Oh and did someone mention it's cheap as well?

however, good on you for having an opinion of your own on the subject. That's what I like about dive forums. Everybody having the ability to ask advice, think it through, sort the wheat from the chaff and then form their own opinion and make their own decisions based on what is right for them.
 
#29 ·
I dive to 50m on air and deco on 70-80 nitrox my reasons for not using trimix is not only the cost of a fill which can often be wasted due to deep dives canned due to the weather change but the cost of getting trainned in the first place (can't get a fill without the badge).Deep dives over 50m seem to be fairly infrequent considering the weather also.
 
#31 ·
I think you may have just had a misunderstanding
Quite agree.

much like your thinking on air /nitrox ,, as for chimpcamp , bunch of guys trying to flog you something .
Seems to me that the OP's thinking on air/nitrox is pretty well spot on. As for "chimp camp", you could well have a fight on your hands if certain parties still frequented this board but you're pretty safe, they don't (more's the pity).

Like you (I suspect) I don't believe that any flavour of SCUBA has every answer but the DIR crowd quite certainly have some of them. No doubt someone else will supplant them at some time from the stage they stride but that time is not yet. Others have some good ideas as well for that matter, but to each his own (and my version of a "good idea" is someone else's disaster-waiting-for-somewhere-to-happen anyway).

The trick, as many have said before me, is to be capable of separating the chaff from the wheat.
 
  • Like
Reactions: burgerbozo
#51 · (Edited)
come on guys, I think everyone is basically in agreement and to summarise the air vs nitrox debate for the OP

The benefits of nitrox over air are lower N2 tissue loading for a given time and depth resulting in a shorter deco obligation (and maybe a little spring in your step from the raised ppO2) and the less narcosis argument is spurious at best.

However people tend not to use nitrox mixes as 'safe air' and dive it using air tables or computers. In the main they use it to extend bottom time with nitrox tables or nitrox computers and either do max duration no stop dives or deco dives. At this point all 'nitrox is safer' arguments have just gone out the window and you are now using nitrox to reduce deco obligation and get out of the water faster. Whether or not the reduction in deco time is worth it depends to a great extent on the length of deco saved with regard to environmental conditions and the amount of gas carried.

To return to the narcosis argument, narcosis is a function of both ppN2 and state of mind (it may be influenced by environmental conditions but from my experience there's something else going on as well) but the dominant factor is ppN2. If you lower the ppN2 at a given depth you lower the narcosis level as well can't argue with that.

However the actual amount of narcosis most people experience at depths where nitrox is commonly used with a ppO2 of <1.4bar ie < 30m ish (36% < 27m, 32% < 33m, (if you use say 27% to get you to 40m you get about a 1 min no stop advantage over air so why bother)) is negligable and many experienced divers won't even notice it.

The downsides of using Nitrox are the added complexity and cost of filling the cylinders and maintaining their O2 clean status for the shops that dont have a nitrox generator and make up mixes by decanting. There is also the risk of a higher percentage mix being used at the wrong depth resulting in oxygen toxicity or a lower percentage mix being used with the wrong table or computer settings resulting in omitted deco. You may actually be less 'safe' using nitrox than air if you don't pay sufficient attention.

Please don't get me wrong. I'm not a dinosaur knocker of nitrox. It definitely has it's uses and I carry a tin of 36% on nearly every dive I do as part of my bailout gas and will happily use it at a ppO2 of 1.6 bar (or more if I have to for a short duration whilst heading up).

You did indeed open up a can of worms with this one that can run and run. :spliff:
 
#52 ·
Thanks Mike. Getting back to the original post as to whether deep air is bad, as has been said 35m isn't really a deep air dive. Once you start going past 40 I guess that's where you can start classing it as deep air but narcosis effects us all differently l know some divers that get seriously narc'd at 35m.

Would nitrox be a safer or less narcotic gas, then no, not really unless you run it on air tables as you will still be going into deco to tick the box so he same pressure group only it will take you longer to get there if running on nitrox tables so you'll have less reserve of gas.

Perhaps you could speak to the instructor and let him know your concerns. Ask him if you can run the dive on nitrox with air tables or run a simulated deco dive, these would be my preferences. If your concern is narcosis (as in deep air) then IMHO it's too shallow to start thinking helium but a I say, everyone's different. Good luck, let us know how it goes.
 
#57 ·
Interesting. I dived same wreck in scapa. Same day. (Dresden). Once on air. Once on nitrox32. May head was slightly clearer on nitrox. I think that was more to do with CO2. Retention than nitrogen imo
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top