Pressure Inside Aircraft Cabin. These valves have to be able to exhaust more CFM of flow than the packs can supply in order to let the cabin climb and when providing less CFM than the packs the cabin will descend. On a typical flight the inside of an airplanes cabin is regulated to a pressure of about 11- 12 psi.
Air is less dense at high altitudes than low altitudes. On a typical flight as the aircraft climbs to 36000 feet the interior of the plane climbs to between 6000-8000 feet. The aircraft window has an area of 810 cm2.
This decrease in oxygen saturation isnt enough to bring on acute mountain sickness.
It might take an average airliner about 20 minutes to reach a cruise altitude of say 35000 feet at which point the pressurization system might maintain the cabin at the pressure youd experience at 7000 feet. Theres also the negative pressure valve which protects the aircraft from the effects of a shift in which the outside pressure would become greater than inside the cabin. Although Boeings Dreamliner technology has lowered that to 6000 feet making the cabin atmosphere more pleasant even though commercial aircraft often fly at 40000 feet. It will relieve that pressure.