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Still young enough to know everything
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Discussion Starter #1
When regulators are rated for a certain percentage of nitrox, is it the partial pressure of oxygen that they have to limit, or the actual percentage? If it is the partial pressure, then is it just the first stages that are limited in the percentage of oxygen, because whether a regulator is good for 40% or 100%, chances are that it will still get a partial pressure of at least 1.4 ATA in it at some point, whereas in the first stage the pressure of a full cylinder is always the same, and so the PPO2 would actually vary, depending on what the percentage is?

Cheers in advance :)
 

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Well Balanced - Bitter and Twisted !!
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Is that it??

Question answer.......????

No ifs buts ???????

James are you feeling ok??

A little more

Yes its the 1st stage thats the real issue as thats where the greatist risk of a problem is, greater pressure changes.

From 0 bar to 232or 300.

More risk of heat being produced.

Fire triangle you need heal fuel and O2, get rid of one no fire.

But if there is O2 already in the nitrox, heat by may be turning the cylinder valve on a bit rapid, all you need is a little bit of fuel then bang.......
Fuel read oil, silicon grease, certain o rings(not for o2 service)swarf , rust almost anything.

If you have Percentage at the surface say 40% thats what people buy nitrox in so there is no confusion.

The pp02 comes into your dive planning
 

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Less oxygen to feed the combustion. The same reason why you fan flames to get a fire going - feed it more oxygen.
 

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Still young enough to know everything
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Discussion Starter #10
Less oxygen to feed the combustion. The same reason why you fan flames to get a fire going - feed it more oxygen.
Yes, but the amount of oxygen that you are breathing changes with depth, so how can there be a fixed percentage that is safe?
 

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Apprentice houseplant
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Because fire cares about %, not ppO2. You care about ppO2.

The inerts reduce the number of collisions between oxygen molecules and potential 'fuel' molecules, thereby reducing the probability of a reaction occurring.
 

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Still young enough to know everything
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Discussion Starter #12
Because fire cares about %, not ppO2. You care about ppO2.

The inerts reduce the number of collisions between oxygen molecules and potential 'fuel' molecules, thereby reducing the probability of a reaction occurring.
But if there are more molecules overall in a particular volume, then the number of collisions with oxygen molecules will be greater - there will also be more collisions with nitrogen molecules and so on, as the concentration of the gas is increasing.
 

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Still young enough to know everything
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Discussion Starter #13
At room temperature and pressure, there is 1 mole of gas in 24l. Lets say that all the gas is pure oxygen. At surface pressure, there is 1 mole of oxygen molecules in that volume. At 10m, or 2 ATA, there is now 2 moles of gas in that volume, so there are twice as many molecules, and so collisions with the oxygen molecules and the container are twice as frequent, without changing the percentage of oxygen in the mix.
 

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Likes rummaging in rust
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But if there are more molecules overall in a particular volume, then the number of collisions with oxygen molecules will be greater - there will also be more collisions with nitrogen molecules and so on, as the concentration of the gas is increasing.
James, it's Saturday ! that's the day after Friday.
 

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Discussion Starter #17
I realise all the stuff about having to be cleaned so there's no crap in it to ignite, but I still don't understand how a particular number of oxygen molecules in a set volume is more dangerous than the same number of oxygen molecules in the same volume of space, but with a few nitrogen molecules or helium atoms thrown in as well.
 

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Jesus don't want me for a sunbeam
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I realise all the stuff about having to be cleaned so there's no crap in it to ignite, but I still don't understand how a particular number of oxygen molecules in a set volume is more dangerous than the same number of oxygen molecules in the same volume of space, but with a few nitrogen molecules or helium atoms thrown in as well.
Just live with it. Flammability goes off percentage and not pO2. At work we have to consider anything higher than 23% O2 as pure O2.
 

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some will tell you 23% is dangerous ,, but if thats the case dive shop cant pump you 32 36 nitron in your crappy tanks ,, mollecules of o2 are ok ,, safe its the speed at witch you move them plus how much shite they hit as they go,, att 200 bar id say f00k it ,, its slow ,, at 500bar id sat fook that you fill your own shitty tank lol
 

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Nigel Hewitt
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The fraction is very important.
For super deep dives where even Helium becomes a problem divers can breath 3% O2 97% H2 and it's just gas.

The mix is so dominated by the hydrogen it won't flash.
 
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