Clean air

[dave archer]

I have a new 12L cylinder on order from my LDS, which will arrive O2 clean.

If I understand things correctly the situation is this:
- there are two classes of air fill, clean and 'unclean'
- if I get a clean fill, my tank is still 02 clean, and I can later use it for nitrox
- if I get an unclean fill, my tank is no longer 02 clean, and I have to get my tank cleaned before I can get a nitrox fill again (how much does this cost BTW?)
- if I attach regs which are not 02 clean to my tank it is no longer nitrox clean

Is that all correct ?

OK, so how common are non O2 clean air fills? For example if I go to Stoney can I get a clean air fill?

Cheers all,
Dave.

[Dominic]

All accurate except for

Originally Posted by [b

Quote[/b] ]- if I attach regs which are not 02 clean to my tank it is no longer nitrox clean

It's clean until it gets a non-clean fill.
IMHO, it's clean even then, but that's not the official line.

Most places these days are doing clean air. The more fills a place does, the more likely clean air is.

[dave archer]

Originally Posted by [b

Quote[/b] (Dominic @ Mar. 25 2004,10:35)]

Cheers Dom, that's the perfect answer as my regs are not O2 clean today.

Why do you say ?

Originally Posted by [b

Quote[/b] ] It's clean until it gets a non-clean fill.
IMHO, it's clean even then, but that's not the official line.

[Richie]

- if I get a clean fill, my tank is still 02 clean, and I can later use it for nitrox
True
if I get an unclean fill, my tank is no longer 02 clean, and I have to get my tank cleaned before I can get a nitrox fill again (how much does this cost BTW?)
Also true - in theory. Cleaning varies £15 ish.
- if I attach regs which are not 02 clean to my tank it is no longer nitrox clean. Not a problem unless you've swished the first stages through a pool of diesel on the way.


OK, so how common are non O2 clean air fills? For example if I go to Stoney can I get a clean air fill?

O2 clean is double filtered or should be and you'll pay extra for this usually. Normal - Stoney type air - is single filtered and will have a higher level if hydrocarbons than the double filtered clean and shiney stuff. Stoney has this but you need to ask for it.

[Dominic]

Originally Posted by [b

Quote[/b] ]Why do you say ?

Numerous reasons - read the "Oxygen Hacker's Companion" for an exhaustive list.

Basically, because the level of caution used by the dive industry about Nitrox is massive overkill.

A normal well-maintained compressor puts out air that qualifies as clean

the hydrocarbon contaminants that they're so worried about don't accumulate fill after fill, they evaporate and come back out with the air

the amount of hydrocarbon you'd need to pose any kind of fire/explosion risk is far greater than the level at which the taste/smell would be detectable by the diver

And so on.

Basically, there's a huge amount of BS about "Oxygen clean".

[Dinger]

Anyway Dave I agree with DOm but if you are feeling flush you can splash out on a personal filter kit for about £250 - £299 or so from DiversWarehouse or DennyDiving - our gang has one that someone got cheap and we all went in together on it but not really sure about the benefit - could be useful as Dom says in a bogging old compressor that fills about 10 tanks a year but other than that bit of overkill
Dinger

[MATTBIN]

Just as a point of interest my LDS services regs to be 02 Clean, which I'm told must be done in a seperate room from non 02 clean ones. Upshot is they do all the regs 02 clean when serviced. My Oceanic DX4 with single second stage no spg etc was done yesterday for £30 all-in. So maybe your shop does the same?

Rgds
Matt

[Fathoms Down]

Originally Posted by [b

Quote[/b] (dave archer @ Mar. 25 2004,10:39)]Cheers Dom, that's the perfect answer as my regs are not O2 clean today.

A tank being O2 clean is different from a reg being O2 clean.

Tanks must be O2 clean if you are putting nitrox in them as there is a possibility that they will be filled using partial pressure blending. This is where the blender fills the tank with pure O2 and tops us with air and so if there is any oil in the tank will probably explode when it comes in contact with the pressurized, pure O2.

Regs must be O2 clean only if you are using gas with high levels of O2 in it. Most regs are fine up to 40% O2 without cleaning but check with your manufacturer so, unless you get into advanced nitrox then your current regs are probably fine.

[dave archer]

Originally Posted by [b

Quote[/b] (Nick Bown @ Mar. 25 2004,12:21)]

A tank being O2 clean is different from a reg being O2 clean.

Tanks must be O2 clean if you are putting nitrox in them as there is a possibility that they will be filled using partial pressure blending. This is where the blender fills the tank with pure O2 and tops us with air and so if there is any oil in the tank will probably explode when it comes in contact with the pressurized, pure O2.

Regs must be O2 clean only if you are using gas with high levels of O2 in it. Most regs are fine up to 40% O2 without cleaning but check with your manufacturer so, unless you get into advanced nitrox then your current regs are probably fine.

Thanks for that Nick, I understand the difference cos of partial pressure filling, and that most regs are OK up to 40%. I am only talking about up 40% too, not into advanced nitrox for deco yet.

Dom, you're probably right that the whole O2 clean thing is overdone, but, say we're being cautious and sticking to the rules....

....if my reg is OK up to 40% when new, but has been used breathing "unclean" air for let's say 100 dives, is it still ok for up to 40% or has the unclean air contaminated it? According to the rules? In reality?

Cheers,
Dave.

[Fiona]

Originally Posted by [b

Quote[/b] (Nick Bown @ Mar. 25 2004,12:21)]Tanks must be O2 clean if you are putting nitrox in them as there is a possibility that they will be filled using partial pressure blending. This is where the blender fills the tank with pure O2 and tops us with air and so if there is any oil in the tank will probably explode when it comes in contact with the pressurized, pure O2.

<font color='#0000FF'>But, if your LDS fills from pre-mixed banks and you have nitrox fills of less than 40% you don't need to have O2 clean cylinders.

FB