1. ventilate 2. Any gas surrounding a given body; a gaseous medium. 3. A unit of air pressure. See also standard a., torr. [atmo- + G. sphaira, sphere]
a. absolute (ata) a unit of absolute pressure (also known as barometric pressure) expressed in atm.
ICAO standard a. the standard a. adopted by the International Civil Aviation Organization, used for calibrating altimeters and for expressing hypobaric chamber pressures in terms of equivalent altitude; it ignores many deviations found in nature.
standard a. (atm) 1. the pressure of the a. at mean sea level, equivalent to 1,013,250 dynes/cm2 or 101,325 Pa (N/m2 in the SI system); 2. a standardized expression of the relation of barometric pressure, temperature, and other atmospheric variables as a function of altitude above sea level.
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