END .Is this correct ?

[colinicky]

Right I know what the formula say's but I always end up lost so please have a good laugh & tell me if this is correct :-

18/45 @ 50m

so I have 0.37 N x 6bar pressure = 2.22ppN

2.22 divide by 0.79 (amount of N in air ) = 2.81which would mean I had an END of 18 metres

Sorry but I can normally work my own way but I get lost with stupid formula's I know I might have the wrong terminology in places

[Janos]

Originally Posted by colinicky

Right I know what the formula say's but I always end up lost so please have a good laugh & tell me if this is correct :-

18/45 @ 50m

so I have 0.37 N x 6bar pressure = 2.22ppN

2.22 divide by 0.79 (amount of N in air ) = 2.81which would mean I had an END of 18 metres

Sorry but I can normally work my own way but I get lost with stupid formula's I know I might have the wrong terminology in places

I think your maths is correct.

However, I treat Oxygen as being narcotic, so for me the Equivalent Narcotic Depth is:

Pressure in bar * (1- %He)
=6 bar * (1-45%)
=6 bar * 55%
=3.3 bar
=23m

Janos

[colinicky]

I think. So realistically even though in the book the formula's look totally different the only difference in including the % of O2 in the workings?

[Richie]

Originally Posted by Janos

I think your maths is correct.

However, I treat Oxygen as being narcotic, so for me the Equivalent Narcotic Depth is:

Pressure in bar * (1- %He)
=6 bar * (1-45%)
=6 bar * 55%
=3.3 bar
=23m

Janos

I understood that the narcotic effect of Oxygen was less than that of Nitrogen - 0.25x IIRC - shouldn't this be factored in?

Probably way off the mark as usual

[johnkendall]

Originally Posted by Richie

I understood that the narcotic effect of Oxygen was less than that of Nitrogen - 0.25x IIRC - shouldn't this be factored in?

Probably way off the mark as usual

One theory relates the narcotic effect of a gas to it's solubility in lipids. This would make Oxygen twice as narcotic as Nitrogen, however we also metabolise oxygen, so this makes a direct comparison quite hard (and we can easily exclude the oxygen to see if that makes a difference)

HTH

John

[Garf]

Originally Posted by Richie

I understood that the narcotic effect of Oxygen was less than that of Nitrogen - 0.25x IIRC - shouldn't this be factored in?

Probably way off the mark as usual

you could, but now things are getting complicated. If we are looking at the solubility model then O2 is actually twice as narcotic as nitrogen. However, the body then metabolises a bunch of it. At this point the maths becomes impossibe.

If you just assume that either a gas is narcotic or it isn't, you always err on the side of safety.

[nigelH]

Originally Posted by colinicky

Sorry but I can normally work my own way but I get lost with stupid formula's I know I might have the wrong terminology in places

May I offer my take on formula.
It might help make things a bit simpler.

[Richie]

Originally Posted by Garf

you could, but now things are getting complicated. If we are looking at the solubility model then O2 is actually twice as narcotic as nitrogen. However, the body then metabolises a bunch of it. At this point the maths becomes impossibe.

If you just assume that either a gas is narcotic or it isn't, you always err on the side of safety.

Complicated indeed.

Thanks for that

[The Doctor]

Originally Posted by Janos

I think your maths is correct.

However, I treat Oxygen as being narcotic, so for me the Equivalent Narcotic Depth is:

Pressure in bar * (1- %He)
=6 bar * (1-45%)
=6 bar * 55%
=3.3 bar
=23m

Janos

How is 02 narcotic please tell or is this some thing you have read on the net.

[johnkendall]

Originally Posted by The Doctor

How is 02 narcotic please tell or is this some thing you have read on the net.

If you look at the Meyer-Overton hypothosis, then Oxygen could be said to have a higher narcotic potential than Nitrogen. However as I said before, since we metabolise it, it's very hard to work out how narcotic it actually is.

It is therefore safest to believe that it is Narcotic, and without any other data, assuming it is as Narcotic as Nitrogen makes the maths easy.

J