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Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101,325 Pa (1,013.25 hPa ), which is equivalent to 1,013.25 millibars , [ 1 ] 760 mm Hg , 29.9212 inches Hg , or 14.696 psi . [ 2 ]
The model, based on an existing international standard, was first published in 1958 by the U.S. Committee on Extension to the Standard Atmosphere, and was updated in 1962, 1966, and 1976. It is largely consistent in methodology with the International Standard Atmosphere , differing mainly in the assumed temperature distribution at higher altitudes.
Decrease in air pressure when going from Earth sea level to 1000 m elevation [citation needed] +13 kPa +1.9 psi High air pressure for human lung, measured for trumpet player making staccato high notes [48] < +16 kPa +2.3 psi Systolic blood pressure in a healthy adult while at rest (< 120 mmHg) (gauge pressure) [44] +19.3 kPa +2.8 psi
= molar mass of Earth's air: 0.0289644 kg/mol The value of subscript b ranges from 0 to 6 in accordance with each of seven successive layers of the atmosphere shown in the table below. The reference value for ρ b for b = 0 is the defined sea level value, ρ 0 = 1.2250 kg/m 3 or 0.0023768908 slug/ft 3 .
Traditionally, compressed air work was limited to maximum ambient pressures of between 3 and 4 bars (3.0 and 3.9 atm), but experience with offshore saturation diving shows that higher pressures can be managed at acceptable risk using the techniques developed in that industry, including saturation exposures and the use of breathing gases other than air.
Originating in ancient India, Vastu Shastra (Sanskrit: वास्तु शास्त्र, vāstu śāstra – literally "science of architecture" [2]) is a traditional Hindu system of architecture [3] [4] based on ancient texts that describe principles of design, layout, measurements, ground preparation, space arrangement, and spatial ...
at each geopotential altitude, where g is the standard acceleration of gravity, and R specific is the specific gas constant for dry air (287.0528J⋅kg −1 ⋅K −1). The solution is given by the barometric formula. Air density must be calculated in order to solve for the pressure, and is used in calculating dynamic pressure for moving vehicles.
Most computerized databases will create a table of thermodynamic values using the values from the datafile. For MgCl 2 (c,l,g) at 1 atm pressure: Thermodynamic properties table for MgCl 2 (c,l,g), from the FREED datafile. Some values have truncated significant figures for display purposes. The table format is a common way to display ...