What is atmospheric pressure?
Atmospheric pressure is the pressure exerted by the atmosphere as a result of gravitational force exerted on the column of air lying directly above. It is commonly measured in units of atmospheres (atm), 1 atm is equal to ~15 lb of force per sq in (~1 kg per sq cm). Sea-level pressure is that atmospheric pressure that occurs anywhere on Earth (actually or fictitiously) at an elevation equivalent to the level of the ocean surface.
