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We have booked to do our Nitrox courses in a couple of weeks and realised that we need to get our cylinders O2 cleaned in order to be filled with O2 enriched air. However, we have since been told that this is not necessary as the cylinders will be filled with a premixed blend. How common is this? and it is worth getting the cylinders cleaned anyway? Is there anything else that we should be aware of when looking for Nitrox fills?
Shmeeg
I've never bothered getting my cylinders O2 cleaned as the 2 places i get fills (Edinburgh Dive Centre and Aquastars in Eyemouth) use a membrain system for making Nitrox. If the place your getting your Nitrox blends in your cylinder then you would be wise to get them O2 cleaned, and the place should really insist on it.
Funny you should mention aquastars!
I am in the same situation as Shog, since we only live about 6 miles apart! Use the same shops!
OHHHHHHHHHHHH can of worms could be opened up here.
Im keeping quiet on this one :rolleyes:
Thanks for the info - we'll just get the tanks cleaned if/when we have to get them filled elsewhere. Looking forward to those longer bottom times (although so far I have been unable to stay in the water longer than 1/2 an hour without my hands getting soo cold they no longer work).
wear warmer gloves-numpty
alexmaclennan
24-06-07, 07:37
OHHHHHHHHHHHH can of worms could be opened up here.
Im keeping quiet on this one :rolleyes:
1. Decide which diveshop you will normally plan to get your nitrox fills from.
2. Ask them what their policy is on nitrox fills and O2 cleaning, specifically will they fill cylinders that have been 02 cleaned elsewhere.
3. Some places will only fill nitrox tanks they have O2 cleaned themselves. If that is the case, and you plan to use that shop, then you will have to pay them to O2 clean your cylinders.
I think the reason is that one form of nitrox production is to put pure O2 into your cylinder and then top up with air. Pure O2 is extremely flammable, so the diveshop could say that they insist on O2 cleaning that tank that they are being asked to fill.
4. There s a lot of heat about the various charges for cylinder testing and turnaround time. My usual diveshop turnaround time for cylinders - my pony is just out of test - was quoted as 5 to 6 weeks yesterday. You would have to check what the cost and turnaround time for O2 cleaning your cylinders were for the shop you plan to use.
alex
alexmaclennan
24-06-07, 09:47
Looking forward to those longer bottom times (although so far I have been unable to stay in the water longer than 1/2 an hour without my hands getting soo cold they no longer work).
Remember nitrox is probably only going to be of value to you, staying down longer, if you are planning deep square profile dives such as on the Clyde wrecks at 30m. Nitrox here will increase your bottom time before going into deco. I rarely go into deco doing our usual two shore dives in Loch Long/ Loch Fyne of a Sunday or during evenings. I initially decided I would dive on Nitrox but gave up on it because fills are more of a hassle than air........of course some will argue that Nitrox leaves you feeling less tired, or increases your safety margin for avoidance of DCS etc. These are different arguments to whether it allows you more bottom time.
alex
If we can get the fills easily, I think the main advantage will be the increased safety margin using Air NDL. I have found myself getting close to the limits quite often with doing 2 boat dives and short surface intervals (which is probably most of our diving). I cringe to think of all the square profile dives I did 15 years ago using 18m/min ascent rates with no knowledge of microbubbles and deep stops. Probably why I'm deaf with a terrible memory (well its a good excuse:rolleyes: )
Yesterday in the forth we dropped down the shot to 28M and did a drift dive flying along between 28-30M if we'd been on air it would have been 20mins max but as we were on EANX32 we got an extra 10 mins :D,on the downside i was wary incase the depth increased as EANX32 has a mod of 33M.
Open water ascent was interesting sending up dsmb whilst trying to dodge the millions of lions mane jellyfish :eek:
Nederlander
24-06-07, 17:54
I did my nitrox ticket a wee while ago and Ive hardly used it.
Have to say that I agree with Alex, its all far too much hassle trying to get filss and all the O2 clean kit having to be kept seperate from yer normal tanks unless your getting Hydrocarbon free air..... BLAH BLAH BLAH.
And then once in the water your crapping yourself in case you go deeper than your MOD,oxygen toxicity....
All that to avoid 10 mins of deco?? I'd rather sit and do the deco myself :p
And its dearer. And you still feel shattered after two dives...
Pointless really???:confused:
I only did it as I was interested in using rich Nitrox fills Eanx 50 and richer to accelerate my deco after long deep dives....
As you can see am not much of a fan of it...
I use nitrox as a matter of preference. For me, the difference in post-dive fatigue is discernible. This is particularly important when I am driving back from dives.
Two deep dives on air, coupled with the early start that most diving trips entail, and I often have to pull over for a nap somewhere. The same sort of profiles on appropriate nitrox mixes produce nothing like the same post dive fatigue.
The sensation may be entirely psychosomatic, and I am aware that there are those out there who feel that nitrox has no proven physiological benefits, but I will take the benefit where I can get it.
I had the opportunity to put this to the test in the past few weeks. Firstly, on a drive back from Oban, after a forty metre dive and a twenty eight metre dive, I had to pull in and nap in a lay-by before I got to Tyndrum. Both the dives were on air.
Last week I did similar dive profiles on EAN28 and EAN32 at the Slates. I did not experience anything like the same post-dive fatigue.
I realise that this is purely anecdotal evidence, but if Nitrox gives you even a psychological advantage that translates into a physical gain then it is a useful tool.
And then once in the water your crapping yourself in case you go deeper than your MOD,oxygen toxicity....
All that to avoid 10 mins of deco?? I'd rather sit and do the deco myself :p
And its dearer. And you still feel shattered after two dives...
Pointless really???:confused:
I only did it as I was interested in using rich Nitrox fills Eanx 50 and richer to accelerate my deco after long deep dives....
deeper than your MOD,... dive planning.
avoiding deco ..... less risk to the diver
do extra deco... you need more gas. exposure to the cold.
more expensive... its not fresh air!
feeling shattered,.... most feel less tired.
pointless... it has its use if you know how to use it.
rich mixes for accelerated deco.... nothing less than a 60% mix is going to have any real speed about it.
deco diving... requires training, or you end up bent!
safe diving.
deeper than your MOD,... dive planning.
avoiding deco ..... less risk to the diver
do extra deco... you need more gas. exposure to the cold.
more expensive... its not fresh air!
feeling shattered,.... most feel less tired.
pointless... it has its use if you know how to use it.
rich mixes for accelerated deco.... nothing less than a 60% mix is going to have any real speed about it.
deco diving... requires training, or you end up bent!
safe diving.
Spot on Stewart ;),i'll be using EANx28 on my deep speciality next weekend
Lizardland
25-06-07, 10:55
rich mixes for accelerated deco.... nothing less than a 60% mix is going to have any real speed about it
Dead right. You're much better off with a decent bottom mix than you are with air and a rich deco mix. For example:
36m for 25min:
- on air, 11min deco but with EAN50 for deco it's 8min
- on EAN32 it's only 2min of deco without the need for extra gas
36m for 45min:
- on air it's 73min of deco
- air & EAN50, 38min of deco
- just EAN32 and nothing else, 32min deco
In both cases your making a bigger saving by using the right bottom gas. If I'm carrying gas for shallow deco stops then I don't bother with anything other than pure O2, EAN50 is a waste of time.
I don't really notice much difference in fatigue between air and nitrox but I have noticed a massive difference since using trimix in my rebreather for shallow diving.
Cheers,
Stuart
EAN32 to 36m sounds a bit too close/beyond the MOD for my liking!
Lizardland
25-06-07, 13:45
EAN32 to 36m sounds a bit too close/beyond the MOD for my liking!
I'm quite happy diving at below 1.5 but each to their own. Even dropping it to EAN30 hardly changes the figures:
25min at 36m on EAN30: 3min of deco
45min at 36m on EAN30: 38min of deco which is still the same as air + EAN50 without the hassle of carrying a gas upon which you're dependant (you really wouldn't want the EAN50 to fail when it's going to double your deco).
EAN32 to 36m sounds a bit too close/beyond the MOD for my liking!
You could actually do 40mtrs on 32% with a PP02 of 1.6 which you probably know is the maximum. Its just accepted to use 1.4 as the benchmark.
36mtrs = 1.5 PP02 with 32%
some good info and best mix/ead and mod calculators here
http://www.ukdivers.net/technical/nitrox.htm
some good info and best mix/ead and mod calculators here
http://www.ukdivers.net/technical/nitrox.htm
v-planner is good too and free for so many days
You could actually do 40mtrs on 32% with a PP02 of 1.6 which you probably know is the maximum. Its just accepted to use 1.4 as the benchmark.
36mtrs = 1.5 PP02 with 32%
not quite,
while 32% @ 40 = 1.6PPO2 its not the maximum as its not what you would plan to dive.
you could go deeper but the pressure increase reduces your exposure time dramatically & to a dangerous level.
high dose, short exposure is acceptable, i.e. 1.6PPO2 while starting your deco, then ascending to the next deco stop where the pressure has reduced.
high dose, long exposure, well..... you might not even feel it.
not quite,
while 32% @ 40 = 1.6PPO2 its not the maximum as its not what you would plan to dive.
you could go deeper but the pressure increase reduces your exposure time dramatically & to a dangerous level.
high dose, short exposure is acceptable, i.e. 1.6PPO2 while starting your deco, then ascending to the next deco stop where the pressure has reduced.
high dose, long exposure, well..... you might not even feel it.
I was meaning that 1.6PP02 is the maximum safe loading as per the course i undertook. But 1.4 was the recommended level which for 32% mix would give me a MOD of 33 mtrs which is all by the by as im still only certed (is that a word :confused: ) to 30 :D