Standard sea-level pressure, by definition, equals 760 mm (29.92 inches) of mercury, 14.70 pounds per square inch, 1,013.25 × 103 dynes per square centimetre, 1,013.25 millibars, one standard atmosphere, or 101.325 kilopascals. Atmospheric pressure can be measured with a mercury barometer (hence the commonly used synonym barometric pressure), which indicates the height of a column of mercury that exactly balances the weight of the column of atmosphere over the barometer. Central Asia, however, is dominated by a strong high-pressure cell. These applications will - due to browser restrictions - send data between your browser and our server. Atmospheric pressure, also known as 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; 1,013.25 mbar), which is equivalent to 760 mm Hg, 29.9212 inches Hg, or 14.696 psi. The table below indicates air pressure at elevations below and above sea level. Articles from Britannica Encyclopedias for elementary and high school students. Altitude above Sea Level and Air Pressure, en: air altitude pressure barometer mercur. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. Learn why the lack of atmospheric pressure in the vacuum of space makes suction cups unusable there. At heights above 1,500 to 3,000 metres (5,000 to 10,000 feet), the pressure is low enough to produce mountain sickness and severe physiological problems unless careful acclimatization is undertaken. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. Do trade winds blow from north to south? You can feel an increase of pressure on your eardrums. Our editors will review what you’ve submitted and determine whether to revise the article. Today only about 0.035 percent of Earth’s atmosphere is carbon dioxide. Examination of data at higher altitudes reveals, however, that the relationship is exponential. Description of pressure and its measurement. The normal air pressure at sea level is 14.7 pounds per square inch. Variations in atmospheric pressure can present special problems for the respiratory systems of animals because atmospheric pressure affects the exchange of oxygen and carbon dioxide that occurs during animal respiration. You can target the Engineering ToolBox by using AdWords Managed Placements. Atmospheric pressure pertains to the downward force applied by the weight of air against a particular area on Earth's surface. Dive down into the ocean even a few feet, though, and a noticeable change occurs. Are aerosols small particles? The pressure at 270,000 metres (10−6 mb) is comparable to that in the best man-made vacuum ever attained.