Pascal (unit) dB SPL, or 20 µPa. The airtightness of buildings is measured at 50 Pa. The units of atmospheric pressure commonly used in meteorology were formerly the bar, which was close to the average air pressure on Earth, and the millibar. Since the introduction of SI units, meteorologists generally measure pressures in hectopascals (hPa) unit, equal to 100 pascals or 1 millibar. Exceptions include Canada, which use kilopascals (kPa). In many other fields of science, the SI is preferred, which means Pa with a prefix (in multiples of 1000) is preferred. Many countries also use the millibars. In practically all other
Pascal (unit) character-sets and are therefore deprecated. The pascal (Pa) or kilopascal (kPa) as a unit of pressure measurement is widely used throughout the world and has largely replaced the pounds per square inch (psi) unit, except in some countries that still use the imperial measurement system or the US customary system, including the United States. Geophysicists use the gigapascal (GPa) in measuring or calculating tectonic stresses and pressures within the Earth. Medical elastography measures tissue stiffness non-invasively with ultrasound or magnetic resonance imaging, and often displays the Young's modulus or shear modulus of tissue in kilopascals. In materials science and engineering,