What is gas pressure and air pressure? What is difference?

Pressure (symbol: p) is the force per unit area applied on a surface in a direction perpendicular to that surface. Mathematically: p=F/A
where:
p is the pressure
F is the normal force
A is the area.
Pressure is transmitted to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point. It is a fundamental parameter in thermodynamics and it is conjugate to volume.

Gas pressure is the pressure of a vapor in equilibrium with its non-vapor phases (i.e., liquid or solid). Most often the term is used to describe a liquid's tendency to evaporate. It is a measure of the tendency of molecules and atoms to escape from a liquid or a solid. A liquid's boiling point corresponds to the point where its vapor pressure is equal to the surrounding atmospheric pressure

The gas pressure is related with the temperature, volume and the number of moles of the gas by PV=nRT
where
P is the pressure in pascals
V is the volume in cubic metres
n is the number of moles of gas
R is the ideal gas constant (8.3145 J/(mol K))
T is the temperature in kelvins.

THE DIFFERENCE BETWEEN GAS PRESSURE AND AIR PRESSURE IS THAT AIR PRESSURE IS ONE KIND OF (SUBSET OF) GAS PRESSURE, ie.WHEN THE GAS IS AIR, THEN THE GAS PRESSURE CONCERNED EQUALS AIR PRESSURE.

Atmospheric pressure is the pressure at any point in the Earth's atmosphere.

In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. Low pressure areas have less atmospheric mass above their location, whereas high pressure areas have more atmospheric mass above their location. Similarly, as elevation increases there is less overlying atmospheric mass, so that pressure decreases with increasing elevation. A column of air 1 square inch in cross section, measured from sea level to the top of the atmosphere, would weigh approximately 14.7 lb. A 1 m² column of air would weigh about 100 kilonewtons.

Standard atmosphere (symbol: atm) is a unit of pressure and is defined as being precisely equal to 101,325 Pa. This value is intended to represent the mean sea level pressure at the latitude of Paris, France, and as a practical matter, approximates the mean sea level pressure for many of the industrialized nations (those with latitudes similar to Paris).

I am sorry that I dont know how to type Chinese, and really cant help you with Chinese ^^

2007-01-01 23:09:39 補充：
Sorry that i dont know how to type chinese
this is a very common comment for me
but i guess i will learn it soon ^^

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2006-12-08 14:42:05 補充：
We, dragon precision industry co. Ltd. Are a specialized manufacturer and supplier of various industrial gas regulators. Among others, we are very specialized in gas regulators for corrosive liquids, precision gas regulators, and high-flow liquid& gas regulators.

Gas Pressure - 氣體壓力;
Air Pressure - 空氣壓力

簡言之, 當有關的氣體為空氣時, 該"氣體壓力" 即等於 "空氣壓力". 你可否告知你在何種情況下見到 / 使用這兩組名詞? 這可有助提供適當的答案.