Why do airplanes pressurize their cabins?

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Discussion Overview

The discussion revolves around the reasons for cabin pressurization in airplanes, exploring the implications for passenger safety and comfort at high altitudes. Participants touch on various aspects including physiological effects, regulatory requirements, and personal experiences related to non-pressurized flights.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that cabin pressurization is essential for preventing hypoxia, as unpressurized cabins would lead to severe health risks for passengers and crew.
  • Others mention the necessity of maintaining breathable air density and the economic factors involved in heating and recycling cabin air, which may contain pollutants.
  • A participant shares a personal experience of flying in a non-pressurized cabin, noting the altitude and pressure changes, and reflects on the lack of complaints from passengers despite the situation.
  • Several contributions highlight the physiological strain of rapid ascents to high altitudes, with references to personal experiences in skydiving and the effects of altitude on individuals in varying physical conditions.
  • Regulatory aspects are introduced, with references to FAA rules regarding the use of supplemental oxygen at specific altitudes, emphasizing the safety protocols for pilots and passengers.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of cabin pressurization for safety, but there are varying perspectives on the implications of non-pressurized flights and the physiological effects of altitude changes. The discussion remains unresolved regarding the adequacy of current regulations and practices.

Contextual Notes

Some claims depend on specific definitions of altitude and pressure, and there are unresolved questions about the adequacy of oxygen supply and the physiological limits of individuals at high altitudes.

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Why do airplanes pressurize their cabins?
 
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Because if they didn't, most of the passengers and crew would die.
 
They have to, so that the air inside is dense enough to provide breathable (Oxygenized) air for the passengers. It costs money to heat this outside air from ambient temperature to cabin temperature, so the airlines routinely "recycle" most of the air, forcing passengers to breathe air that is loaded with environmental pollutants and pathogens.
 
See what happened to Payne Stewart. That's why planes are pressurized for those that don't have portable oxygen tanks next to them.
 
I flew in a non-pressurized cabin once. Detroit to chicago; at about 10 minutes into the flight they told us they couldn't get the cabin to pressurize. They said they'd be flying a lot lower to try to help and to let them know (as if they could do something about it) if they were any problems.
I figure they only flew at say 14-16k feet, which i think would be about 21inHg. (so about a 27-28% drop in pressure?)

Wasn't so bad. Did the opposite ears-popping thing, other than that it was fine. I wonder if they turned up the O2 or anything. I don't think anyone on board complained at all.
 
I'm in pretty good shape, but when I went skydiving, my instructor said I was turning white and gave me oxygen. I think a rapid ascent from sea level to 13,500 feet can be a strain.
 
russ_watters said:
I'm in pretty good shape, but when I went skydiving, my instructor said I was turning white and gave me oxygen. I think a rapid ascent from sea level to 13,500 feet can be a strain.
Even ascending a mile-high mountain can stress people if the climb is steep and they are not in shape, so a rapid change to nearly 3 times that altitude in an unpressurized plane should have some effects on some folks, especially if your pumped about the prospect of jumping out of the thing and your metabolic rate is a bit high.
 
SOP for us was to stay below 10,000 ft without supplemental oxygen. I believe most emergency procedures call out the 10,000 ft altitude as the level to get below asap.
 
FAA rules:

Oxygen must be used by a pilot any time above 14,000 feet and above 12,500feet in excess of 30 minutes. (What about the passengers?).

A full fitting face mask must be used above 18,000 feet. The percentage of oxygen increases with altitude. It's 100% at around 43000 feet.

Above 43,000 feet, the pressure is too low for even 100% oxygen to do the job, so a pressurized system is required (suit or cabin).
 

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