low pressure effects on us

SixPapaCharlie

SixPapaCharlie

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I have not tried this but I would assume if I took a sealed balloon on a GA plane, as I ascend, it will inflate. :dunno:

Would it be noticeable or is it more subtle?
How many feet to make an obvious change?
I have heard of potato chip bags popping on flights before.

The next part of the question is how this pressure change affects parts of us. Our ears pop but what about our eyes? Do they expand as altitude goes up? I don't notice myself burping more in the sky but I would assume as we ascend, there should be expansion throughout.

I didn't think to get an explanation but in the pressure chamber in hindsight, I want to know the affect of going to 24k feet has on my eyes. I am assuming they are essentially sealed balloons and as such should expand.

I am going to try the balloon thing sometime just to see if I notice in inflate from the ground to 10k feet but more interested in knowing how this affects our bodies.
 
You might also try the plastic water bottle thing. Seal the cap on it while at a higher altitude and then watch it crush a little bit as you descend...

As for the eye thing, now you've got me curious too...
 
Eyes are filled with incompressible fluid. Nothing will happen besides them drying out a bit faster.
 
N321SR said:
Eyes are filled with incompressible fluid. Nothing will happen besides them drying out a bit faster.
Click to expand...

Ascending wouldn't cause compression but rather expansion correct?
So (And I plead ignorance here) could we not get air bubbles in our eyes?
 
Fluids (water) do not appreciably change volume with changing pressure so your eyes won't expand and contract as a volume of gas would with changing pressure. There most certainly would be gases dissolved in your eye fluid but since they are in solution they would also be incompressible also. I do not know if decreasing pressure could cause the gasses to come out of solution as happens with divers experiencing the bends or not but I've never heard of it happening.
 
Had a chip bag pop on way to Oshkosh last year. We both heard it. We knew what is was though.

Joe
 
Gonna fart a lot more... well some more maybe.
 
SixPapaCharlie said:
I have not tried this but I would assume if I took a sealed balloon on a GA plane, as I ascend, it will inflate. :dunno:

Would it be noticeable or is it more subtle?
How many feet to make an obvious change?
I have heard of potato chip bags popping on flights before.

The next part of the question is how this pressure change affects parts of us. Our ears pop but what about our eyes? Do they expand as altitude goes up? I don't notice myself burping more in the sky but I would assume as we ascend, there should be expansion throughout.

I didn't think to get an explanation but in the pressure chamber in hindsight, I want to know the affect of going to 24k feet has on my eyes. I am assuming they are essentially sealed balloons and as such should expand.

I am going to try the balloon thing sometime just to see if I notice in inflate from the ground to 10k feet but more interested in knowing how this affects our bodies.
Click to expand...
Yes, the balloon will inflate, or more accurately it will expand and that expansion will be obvious. Here is a site where you may enter an altitude and see a percent decrease in ambient pressure:
http://www.altitude.org/air_pressure.php

The second part of your question has been answered correctly. Liquids such as within the eye are not compressible. There are some rare cases where one may have an air bubble inside the globe of the eye such as a month or so after eye surgery. In those rare cases, that air bubble would be subject to expansion with altitude.
 
What's been said is about right in that:

1. Yes, assuming constant temperature (ie you have a heater on in the cabin), Boyle's law means that if you take a contained gas parcel like a balloon or chips bag to altitude, the air inside will expand with decreasing pressure. Pressure * Volume = constant. As for how much (by how many times) a given bit of gas would expand, plug your altitude in here.

2. Most liquids we think of generally, and water specifically, is relatively incompressible. So all of the air in your body will expand a bit, but your watery watery eyes won't explode. Ask any scuba diver where the air is in your body, but the general rules are: lungs (if you try to hold your breath to 18,000 feet in a zoom climb, you'll hurt yourself), sinuses and ears (go flying on a really congested day and you'll feel it), gut (yes, you can get a bit of gas at altitude), dental fillings if you're unlucky (if your teeth hurt when you fly, that's why), recent surgical sites, etc.

3. Completely separately from point 1, which deals with gasses already in gas form, gasses that are dissolved in liquids "want" to come out of solution in low pressure environments. (The constant vapor pressure of the gas at given temperature has less outside pressure to compete with.) That's why water boils at a lower temperature in Denver. For most human physiology purposes, that doesn't matter much, unless you have an abnormally large amount of gas dissolved in your fluids (because you've been scuba diving recently) or you are going to outrageously high altitude (like these guys, who had to pre-breathe oxygen to get rid of the nitrogen dissolved in their bodies, as well as wear pressure suits).
 
I occasionally notice increased urination above 12,000'.
 
opened a seltzer bottle at 11k without giving it much thought the other day. Took a while to dry things out after that.

Later opened another one, more slowly...took 60-90 secs of slow release to get it fully opened. Hard doing it by sight only, normally I rely on the sound :)
 
SixPapaCharlie said:
I have not tried this but I would assume if I took a sealed balloon on a GA plane, as I ascend, it will inflate. :dunno:
Click to expand...
You assume correctly.
Would it be noticeable or is it more subtle?
Click to expand...
Depends how fast/high you climb, but eventually you will see a significant change.
How many feet to make an obvious change?
Click to expand...
:dunno:
I have heard of potato chip bags popping on flights before.
Click to expand...
I've had it happen myself at about 12,000 feet. Got my attention.

The next part of the question is how this pressure change affects parts of us. Our ears pop but what about our eyes? Do they expand as altitude goes up?
Click to expand...
Eyes are filled with liquid, which does not expand the same way as a gas.

I don't notice myself burping more in the sky but I would assume as we ascend, there should be expansion throughout.
Click to expand...
Depends how much gas there is in your gut, and where in your gut it is. I just about killed the guys next to me in the pressure chamber at Wiesbaden when I had the all-you-can-eat Mexican dinner at the Wiesbaden O'Club the night before my triennial physiological training in 1987.

I didn't think to get an explanation but in the pressure chamber in hindsight, I want to know the affect of going to 24k feet has on my eyes. I am assuming they are essentially sealed balloons and as such should expand.
Click to expand...
They are completely filled with liquid, not gas. That's why a completely-filled water bottle won't pop its top, but if it's only half full it will.

I am going to try the balloon thing sometime just to see if I notice in inflate from the ground to 10k feet but more interested in knowing how this affects our bodies.
Click to expand...
Should be instructive. For military physiological training, they always hang a balloon or latex glove or something in the pressure chamber so we can watch it expand on the way up and contract on the way down.
 
coma24 said:
opened a seltzer bottle at 11k without giving it much thought the other day. Took a while to dry things out after that.

Later opened another one, more slowly...took 60-90 secs of slow release to get it fully opened. Hard doing it by sight only, normally I rely on the sound :)
Click to expand...
Note that a bottle of carbonated beverage is not the same as a bottle of still beverage. If you have pressure in the bottle and open the cap, it's going to geyser, but with a bottle full of still liquid (no gas volume at the top), nothing much happens at all.

It's like the difference between opening a bottle of still wine versus sparkling wine. When you pull the cork on the still wine, you get a pop because as you extract the cork, you're expanding the volume of trapped air at the top of the bottle, reducing the pressure inside until the cork clears the mouth and the outside air rushes in with a "pop". OTOH, sparkling wine is under pressure in the bottle to keep the CO2 in solution. You can feel the pressure pushing the cork, and when the cork clears the mouth, the pressurized gas in the bottle rushes out with a "pop", followed by the CO2 in the wine coming out of solution and foaming the wine.
 
We stopped at a convenience store at a high elevation somewhere a couple years ago on a long car trip. Inside, there was display of Pringles. Most of the plastic lids had been popped off as the foil seals on the top of the tubes had expanded from wherever they had been packed.
 
coma24 said:
opened a seltzer bottle at 11k without giving it much thought the other day. Took a while to dry things out after that.

Later opened another one, more slowly...took 60-90 secs of slow release to get it fully opened. Hard doing it by sight only, normally I rely on the sound :)
Click to expand...


I live at 6500 feet. Opening carbonated bottles correctly is something learned the hard way. And yes, suddenly the thing spews before you see anything.

When we go grocery shopping, anything that comes in a sealed package is checked first then into the cart or back on the shelf.

I used to fly supplies over a mountain pass in Alaska. Nothing like a quick pop and then Doritos flying all over the plane. :lol:
 
SixPapaCharlie said:
I have not tried this but I would assume if I took a sealed balloon on a GA plane, as I ascend, it will inflate. :dunno:

Would it be noticeable or is it more subtle?
How many feet to make an obvious change?
I have heard of potato chip bags popping on flights before.

The next part of the question is how this pressure change affects parts of us. Our ears pop but what about our eyes? Do they expand as altitude goes up? I don't notice myself burping more in the sky but I would assume as we ascend, there should be expansion throughout.

I didn't think to get an explanation but in the pressure chamber in hindsight, I want to know the affect of going to 24k feet has on my eyes. I am assuming they are essentially sealed balloons and as such should expand.

I am going to try the balloon thing sometime just to see if I notice in inflate from the ground to 10k feet but more interested in knowing how this affects our bodies.
Click to expand...

On my first X/C with a passenger with a 3 week old pilot's certificate, i forgot that a water bottle sealed at sea level would be under more pressure at 9500 feet.. Exploded in my face, covered me in water .
 
SixPapaCharlie said:
I have not tried this but I would assume if I took a sealed balloon on a GA plane, as I ascend, it will inflate. :dunno:
Click to expand...
A rubber balloon will get a bit larger as you ascend. I wouldn't try this with a mylar balloon however, the mylar doesn't "give" like rubber will. As you ascend, the balloon will pop, and rather loudly.
 
Yep I've had a bag of chips get so big I was afraid to open it while in an airliner. It was ready to explode and had me worried.

I SCUBA dive and the one thing they drilled into you in training is do not ever hold your breath. Take a balloon, as you descend the pressure causes the balloon to get smaller, as you ascend the balloon goes back to normal. So if you held your breath while diving and ascend pop goes the lungs. Only air spaces are affected by pressure, ears, lungs, sinuses.
 
1) This was sunscreen:

8294505630_48cbb6d199.jpg


Honest. :redface:

2) Did not pop, but I think it was close:

15149259129_910af0fecb.jpg


3) If you ever have helium filled mylar balloons in your car unsecured, watch what happens when you hit the brakes!
 
Along these lines, a thermos of coffee opened at altitude will get your attention right quick. The boiling point of liquid goes down with altitude. Fill up your thermos with hot coffee on the ground....open at altitude and it'll come out at you boiling......

(for you filthy, dirty smokers (present company included) don't even THINK about using a disposible Bic lighter):yikes:
 
the balloon will go backwards because helium is lighter than air and the air will go forwards?
 
When I was in high school I worked second shift at the BiltBest Windows factory in my home town.

They got their first big order for windows out west when I was a junior. They were going to a ski lodge in Colorado. Which one, I don't recall. When the order arrived and they opened the truck, all the insulated, double pane, glass lites had exploded, every one.

Oops.

A fix was developed pretty quickly and we started cranking out "high altitude" double pane windows.
 
sferguson524 said:
On my first X/C with a passenger with a 3 week old pilot's certificate, i forgot that a water bottle sealed at sea level would be under more pressure at 9500 feet.. Exploded in my face, covered me in water .
Click to expand...
Just be glad it wasn't your pee bottle.
 
Ron Levy said:
Just be glad it wasn't your pee bottle.
Click to expand...

For SURE!!!! I tend to bring those piddle paks with me when i go on longer trips, the kind that turn liquid to gel. They double quite well as barf bags too
 
SixPapaCharlie said:
Ascending wouldn't cause compression but rather expansion correct?
So (And I plead ignorance here) could we not get air bubbles in our eyes?
Click to expand...

Compression/expansion - it's just a sign difference. The compressibility of water is negligible across the pressure range seen in flight.

The compressibility of water at around atmospheric pressure is

3.12 x10^-6 cc/cc/psi (this number holds true for any unit of measure: gallons/gallon/psi, liters/liter/psi, etc. Units arevolume/volume/psi or psi^-1)

So one psi of pressure change (greater or smaller) changes the volume of a cc of water by + or - 3.12 x10^-6 cc. So it is virtually incompressible or expandable.

TMI:

In petroleum reservoir engineering (my discipline) the compressibility of water is a factor when you have extremely large volumes of saline water at very high pressures that are subjected to large pressure differentials (like when you drill into the reservoir and allow fluids to flow). It can actually be a factor in the reservoir drive mechanism. Other factors are gas, oil, and rock compressibility. As you might imagine, gas would be the most compressible/expandable if present - by several orders of magnitude. So it would take a reservoir with very little gas and a whole lot of water for the water expansion to be much of a factor in the overall reservoir drive.

SixPapaCharlie said:
the balloon will go backwards because helium is lighter than air and the air will go forwards?
Click to expand...

Correct.

I did that experiment one time with my kids on the way back from Red Robin. Take off from a stop light and the balloon leans forward if it is fixed to the floor.

___________________

I use one of those squirt bottles in flight that has the little silicone valve where it won't leak unless squeezed - not sure what to call it. During flight my water bottle sits there in my console and "poofs" every so often as the pressure difference increases between the inside/outside. If I were to lay it down then it would sit there and push liquid out instead of "poofing". So I have to make sure it is upright-ish so that doesn't happen.

I once let my kids use a water bottle like that and they laid it down and I got a small puddle of water on the carpet. Now they don't get drinks until we level off. :mad2:
 
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weirdjim said:
Were you flying out of Temecula International Peapatch when the runway end and the end of Main Street were only separated by a barbwire fence?

Fun little airport to get a student to land upon.

Jim
Click to expand...

No, I moved there in '03. F70 was already in use. I have done most of my flying out of MYF.
 
N321SR said:
LIQUIDS (water) do not appreciably change volume with changing pressure so your eyes won't expand and contract as a volume of gas would with changing pressure. There most certainly would be gases dissolved in your eye fluid but since they are in solution they would also be incompressible also. I do not know if decreasing pressure could cause the gasses to come out of solution as happens with divers experiencing the bends or not but I've never heard of it happening.
Click to expand...

FTFY :D
 
weirdjim said:
I split my time teaching out of MYF and SEE. Of course that was when 27 was a single runway and 23 was dirt.

Dirt. Not grass. Dirt.

Jim
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That's pretty awesome.. Do you have pics from back in the day? My CFII is still at MYF and would get a kick out of it
 
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