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Inch of mercury (inHg and ″Hg) is a non-SI unit of measurement for pressure. It is used for barometric pressure in weather reports , refrigeration and aviation in the United States . It is the pressure exerted by a column of mercury 1 inch (25.4 mm) in height at the standard acceleration of gravity .
The torr is defined as 1 / 760 of one standard atmosphere, while the atmosphere is defined as 101325 pascals. Therefore, 1 Torr is equal to 101325 / 760 Pa. The decimal form of this fraction ( 133.322 368 421 052 631 578 947 ) is an infinitely long, periodically repeating decimal ( repetend length: 18).
inHg ≡ 13 595.1 kg/m 3 × 1 in × g 0: ≈ 3.386 389 ... torr: torr ≡ 101 325 ...
1 torr ≈ 1 mmHg [34] ±200 Pa ~140 dB: Threshold of pain pressure level for sound where prolonged exposure may lead to hearing loss [citation needed] ±300 Pa ±0.043 psi Lung air pressure difference moving the normal breaths of a person (only 0.3% of standard atmospheric pressure) [35] [36] 400–900 Pa 0.06–0.13 psi
BS 1042:1:1964 notes that the "conventional pressure of 30 inHg is based on the conventional density of mercury (13.5951 g/cm 2) at 0 o C" but also lists a reference pressure of 30 inHg that was "the pressure due to a 30 inch column of mercury at 60 o F under an acceleration of free fall of 32.1740 ft/s 2" adding "This reference unit of ...
Torr Torr 1.0 Torr (0.13 kPa) millimetre of mercury: mmHg mmHg 1.0 mmHg (0.13 kPa) inch of mercury: inHg inHg 1.0 ...
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]
A torr was originally defined as 1 mmHg. The pressure is quoted as the level of the mercury's height in the vertical column. Typically, atmospheric pressure is measured between 26.5 inches (670 mm) and 31.5 inches (800 mm) of Hg. One atmosphere (1 atm) is equivalent to 29.92 inches (760 mm) of mercury.