Air Pressure
Air has mass, density, and pressure.
Air pressure is the result of a column of air pushing down in an area. You don’t feel it, because it pushes in all directions. A barometer is an instrument that measures air pressure. Altitude, or elevation, is the distance above sea level. As altitude increases, air pressure decreases.
As altitude decreases, air pressure increases. (Think of a stack of books.)
As altitude increases and air pressure decreases, density of the air also decreases. The air has less oxygen, so it is harder to breathe.
­Column of
air = air
pressure
­Less pressure
­Bigger column =
more pressure
Density­the
amount of mass
in a certain
volume.
Sea level
0' altitude
Low altitude High altitude
78% nitrogen
21% oxygen
Below sea level ­100' altitude
78% nitrogen
21% oxygen
It is harder to breathe at high altitudes
because there is less oxygen in the air. However, the PERCENT of oxygen is the same.
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