Many coffee machines use pressure to enhance brewing parameters. Some of the devices that use pressure are single serve coffee machines, such as Keurig, or Tassimo, and espresso machines. Other devices are the Moka pot, or steam espresso makers. Pressure is measured in bar.
The bar is a non-SI unit of pressure, defined by the IUPAC as exactly equal to 100,000 Pa. It is about equal to the atmospheric pressure on Earth at sea level, and since 1982 the IUPAC has recommended that the standard for atmospheric pressure should be harmonized to 100,000 Pa = 1 bar ≈ 750.0616827 Torr. The same definition is used in the compressor and the pneumatic tool industries (ISO 2787).