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Air Pressure Inside
Airplane Cabins
The article How Tire Pressure Gauges Work explains air pressure.
The atmosphere is about 50 miles
"deep," and at sea level it exerts 14.7 pounds per square inch (psi).
Our bodies think 14.7 psi is
completely normal.
When you blow up a tire on
a car or a bike, you use a pump to increase the pressure
inside a closed space.
A car tire typically runs at
30 psi, and a bike tire might run at 60 psi. There is no magic here -- the pump
simply stuffs more air into a constant
volume so the pressure rises.
A plane flies at about 30,000
feet.
The air pressure at 30,000
feet is significantly lower than at sea level (4.3 psi versus 14.7 psi).
High-pressure air is used to
"pump up" the cabin in much the same way that a tire is pumped up.
The high-pressure air on most
planes comes from the compression stage of the jet engines.
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