Partial Pressures and Depth Question

[boulderjohn]

But what about technical diving? can we do the same? No we cant. because our organs are Saturated. Maxed out.

Correct me if I'm wrong, but you sound like you are taking about saturation as if the tissues were like a bucket of water that is full to the brim. A tissue that is saturated has simply reached equilibrium at that depth. It is not maxed out. If it went deeper, it would not longer be at equilibrium, and it would take on more nitrogen.

 

[LanceRiley]

An Introduction to Scuba Gas Laws - Part 3: Henry’s Law - DeepDive

Henry’s Law William Henry was an English physician and chemist who, in 1803, proposed what is now called Henry’s law. This law states that “At a constant

www.scuba.com

pressure plays a part …..

 

[LanceRiley]

Correct me if I'm wrong, but you sound like you are taking about saturation as if the tissues were like a bucket of water that is full to the brim. A tissue that is saturated has simply reached equilibrium at that depth. It is not maxed out. If it went deeper, it would not longer be at equilibrium, and it would take on more nitrogen.

trying to explain it as simple as possible thats all.

I use saturated as max out. if its saturated it means it cant take anymore cant it? for that given pressure

 

[LanceRiley]

This is incorrect and I think the crux of your misunderstanding of the processes.

When you bring two different gasses into contact, it's their relative concentration, aka concentration gradient, that drives diffusion. Concentration simply means the number of molecules of each substance per given area, Differences in pressure only matter to diffusion because, for gases, higher pressure means a greater difference in concentration.

It may help to bring this back to first principles. Unlike solids, gas molecules are constantly zipping around in random directions. If you've got only x molecules in one spot and y molecules in another, then from the first zip they are going to start intermingling. With each subsequent zip, around half the molecules will further move away from their initial point of concentration. It doesn't take that many zips before the concentration differences have disappeared. We call this equilibrium, but it's a mistake to think of it as static. The molecules continue to zip around, causing variations in concentration in any particular tiny volume.

I think I should link this here: Fick's laws of diffusion - Wikipedia

Of course, if you put some sort of barrier between the two gasses, this process will slow. But it won't stop if there is any possible movement across the barrier. In your case of the gas tanks connected by a hose (of reasonable length), the tanks will reach equilibrium within several hours, maybe even a day, but certainly not "forever".

the gas tanks were there as an example that without a pressure difference… it would take forever….

someone insisted that pressure doesnt play a part in offgassing

 

[LanceRiley]

Decompression theory - Wikipedia

en.m.wikipedia.org

this here

 

[boulderjohn]

someone insisted that pressure doesnt play a part in offgassing

No one said that.

 

[LanceRiley]

ill have to look at the replies. someone mentioned that pressure doesnt play a part in offgassing. thats why were discussing pressures

tried to explain it as simple as possible without going into technical.

 

[boulderjohn]

ill have to look at the replies. someone mentioned that pressure doesnt play a part in offgassing. thats why were discussing pressures

When I was discussing pressures, I was simply trying to use clarifying language for the general population. When we normally speak of pressures, we think of something like the water pressure in our house sending out spurts of water. We think of something that provides a push. In my experience as an instructor, students simply don't understand what we mean by gas pressure and pressure gradients because that is how they think of pressure.

I found it works much better to talk about diffusion and what Ron described as the concentration of the gas. It is just an attempt to describe what actually happens in language that makes sense to new learners.

 

[David Carron]

ill have to look at the replies. someone mentioned that pressure doesnt play a part in offgassing. thats why were discussing pressures

tried to explain it as simple as possible without going into technical.

Absolute ambient pressure does not play a direct part in on/off gassing.

The only thing that counts is the difference between the inert gas partial pressures in the lungs and the rest of the body. This is why at the same absolute ambient pressure you offgas faster breathing oxygen than breathing air.

 

[LanceRiley]

When I was discussing pressures, I was simply trying to use clarifying language for the general population. When we normally speak of pressures, we think of something like the water pressure in our house sending out spurts of water. We think of something that provides a push. In my experience as an instructor, students simply don't understand what we mean by gas pressure and pressure gradients because that is how they think of pressure.

I found it works much better to talk about diffusion and what Ron described as the concentration of the gas. It is just an attempt to describe what actually happens in language that makes sense to new learners.

well i guess it differs in understanding for every region most newbies i describe it that way with a bit of suggestion…. if you wana learn more take a class