8 ms·

Even with a canister of oxygen, at 35,000 feet you can't breath if you aren't in a pressure suit. Why not?

by pdx 14y ago

brianchu 14y ago
Did you read the article? "At 18,000ft (5,490m), experts say, hypoxia will set in, causing weakness, tremors, light-headedness and visual impairment...Above 33,000ft (10,065m) the lungs require artificial pressure to function normally."
- pdx 14y ago
  Above 33,000ft (10,065m) the lungs require artificial pressure to function normally. So, you don't know either. Why did you respond then? The pressure from an oxygen canister can be down regulated to anything you choose, including 1ATM.
  - praptak 14y ago
    I doubt that human lungs can withstand this much difference between inside and outside pressure. I haven't found the maximum non-harmful difference but a quick google found that maximum expiratory pressure in men is 97 cmH2O. This is only about 0.08 atm. So I wouldn't count on the canister alone, unless it is connected to a full-body suit.
ChuckMcM 14y ago
Your lungs need a minimum density of air in order for the gas to pass into your blood. If you can't maintain that air density you 'outgas' only. It won't kill you immediately (you can actually survive in a complete vacuum for example) until the existing oxygen in your system runs out, then its game over.
- mukaiji 14y ago
  I don't believe you can survive in a true vacuum. Your skin would bruise instantly for one.
  - joezydeco 14y ago
    Some anecdotal evidence here: http://www.geoffreylandis.com/vacuum.html http://www.geoffreylandis.com/vacuum.html
  - Someone 14y ago
    Even if that is true, why do you think skin bruising is lethal? Unsurprisingly, there is little data on this, but what there is seems to indicate that vacuum is survivable.see e.g. http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.h..., http://www.newscientist.com/blog/space/2008/06/how-long-can-you-survive-in-vacuum-of.html http://www.newscientist.com/blog/space/2008/06/how-long-can-...
refurb 14y ago
Partial pressures. You can breath at 35,000 ft without a pressured suit, but go much higher and you can't. At sea level, you have 760 mmHg of air pressure. Oxygen is 21% of the air mixture, so you have a partial O2 pressure of 160 mmHg. At 35,000 ft, air pressure is 179 mmHg [1], so if you breath 100% pure oxygen, you're getting the same amount of oxygen you'd get at sea level. Go up to 50,000 ft and the air pressure is only 83 mmHg, so even breathing 100% oxygen, you're only getting 50% of the oxygen you'd get at sea level. [1] http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html http://www.engineeringtoolbox.com/air-altitude-pressure-d_46...
- pdx 14y ago
  The OP said you needed a pressure suit, and that an O2 canister wouldn't help. Since the pressure of the O2 cannister will be down regulated to 1ATM, I can breath 1ATM air, no matter where I am, including 35,000 feet. Is there, perhaps, some reason why I can't? Lungs exploding because of the 1ATM pressure differential, for instance? It seems that 1ATM is not that much, but perhaps it is... That's what I'm curious about.
  - refurb 14y ago
    You can breath pressurized air directly from an air mask without wearing a pressurized suit. Many military aircraft use this system (the air mask is strapped tightly to the face to maintain pressure). I'm sure at some point you need a pressurized suit to make breathing possible, but it likely has more to do with preventing decompression sickness and protecting against the cold (at very low pressure the moisture from your skin will rapidly boil, cooling off your skin).
    - pdx 14y ago
      I found this. Towards the end, it starts talking about positive pressure respiration at high altitude. http://webs.lanset.com/aeolusaero/Articles/A_Brief_History_of_US_Military_Aviation_Oxygen_Breathing_Systems.pdf http://webs.lanset.com/aeolusaero/Articles/A_Brief_History_o...

Even with a canister of oxygen, at 35,000 feet you can't breath if you aren't in a pressure suit. Why not?

by pdx 14y ago

Even with a canister of oxygen, at 35,000 feet you can't breath if you aren't in a pressure suit. Why not?

Did you read the article? "At 18,000ft (5,490m), experts say, hypoxia will set in, causing weakness, tremors, light-headedness and visual impairment...Above 33,000ft (10,065m) the lungs require artificial pressure to function normally."

pdx 14y ago
Above 33,000ft (10,065m) the lungs require artificial pressure to function normally. So, you don't know either. Why did you respond then? The pressure from an oxygen canister can be down regulated to anything you choose, including 1ATM.
- praptak 14y ago
  I doubt that human lungs can withstand this much difference between inside and outside pressure. I haven't found the maximum non-harmful difference but a quick google found that maximum expiratory pressure in men is 97 cmH2O. This is only about 0.08 atm. So I wouldn't count on the canister alone, unless it is connected to a full-body suit.

ChuckMcM 14y ago

Your lungs need a minimum density of air in order for the gas to pass into your blood. If you can't maintain that air density you 'outgas' only. It won't kill you immediately (you can actually survive in a complete vacuum for example) until the existing oxygen in your system runs out, then its game over.

mukaiji 14y ago
I don't believe you can survive in a true vacuum. Your skin would bruise instantly for one.
- joezydeco 14y ago
  Some anecdotal evidence here: http://www.geoffreylandis.com/vacuum.html http://www.geoffreylandis.com/vacuum.html
- Someone 14y ago
  Even if that is true, why do you think skin bruising is lethal? Unsurprisingly, there is little data on this, but what there is seems to indicate that vacuum is survivable.see e.g. http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.h..., http://www.newscientist.com/blog/space/2008/06/how-long-can-you-survive-in-vacuum-of.html http://www.newscientist.com/blog/space/2008/06/how-long-can-...

refurb 14y ago

Partial pressures. You can breath at 35,000 ft without a pressured suit, but go much higher and you can't. At sea level, you have 760 mmHg of air pressure. Oxygen is 21% of the air mixture, so you have a partial O2 pressure of 160 mmHg. At 35,000 ft, air pressure is 179 mmHg [1], so if you breath 100% pure oxygen, you're getting the same amount of oxygen you'd get at sea level. Go up to 50,000 ft and the air pressure is only 83 mmHg, so even breathing 100% oxygen, you're only getting 50% of the oxygen you'd get at sea level. [1] http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html http://www.engineeringtoolbox.com/air-altitude-pressure-d_46...

pdx 14y ago
The OP said you needed a pressure suit, and that an O2 canister wouldn't help. Since the pressure of the O2 cannister will be down regulated to 1ATM, I can breath 1ATM air, no matter where I am, including 35,000 feet. Is there, perhaps, some reason why I can't? Lungs exploding because of the 1ATM pressure differential, for instance? It seems that 1ATM is not that much, but perhaps it is... That's what I'm curious about.
- refurb 14y ago
  You can breath pressurized air directly from an air mask without wearing a pressurized suit. Many military aircraft use this system (the air mask is strapped tightly to the face to maintain pressure). I'm sure at some point you need a pressurized suit to make breathing possible, but it likely has more to do with preventing decompression sickness and protecting against the cold (at very low pressure the moisture from your skin will rapidly boil, cooling off your skin).
  - pdx 14y ago
    I found this. Towards the end, it starts talking about positive pressure respiration at high altitude. http://webs.lanset.com/aeolusaero/Articles/A_Brief_History_of_US_Military_Aviation_Oxygen_Breathing_Systems.pdf http://webs.lanset.com/aeolusaero/Articles/A_Brief_History_o...