Krypton (Kr, from Greek “kryptos” – hidden, concealed) is the fourth of the rare gases, neither flammable nor toxic, and forms a coloress, odorless, monoatomic and chemically inert gas. The density of Krypton amounts to 3.506 kg/m3 at 15 °C / 1000 mbar, while the Krypton gas molar mass equals 83.8 g/mol. It is only found in the atmosphere in traces of 1.14 ppm (1.14 parts per million, roughly 1 out of one million particles) and thus constitutes only a narrow fraction of the air on Earth.

As a major application, Krypton gas is sealed between two panes to manufacture dual pane Krypton filled windows. Such Krypton gas windows exhibit excellent insulating properties due to Krypton’s low heat conductivity while maintaining compact window design. Likewise, specific etching processes in the electronics industry as well as Krypton ion thruster for satellites in the space industry run high purity Krypton as an etchant or propellant, respectively. Although in both cases the performance efficiency is reduced due to the lower molar mass of Krypton gas, it represents a cost-efficient alternative compared to Xenon. Additionally, a Krypton laser (more precisely: a Krypton Fluoride Laser) consumes gas mixtures containing small fractions of Krypton.