The report describes a rapid method for determining 85Kr in environmental air samples. Equipment and procedure used to separate 85Kr from environmental air samples for liquid scintillation counting are described in detail. The procedure employs charcoal and molecular sieve cold traps, calcium sulphate, ascarite (NaOH preparation) and a titanium furnace (900C) for the removal and separation of other air constituents from krypton. Air samples are spiked with 83Kr(m) to provide a direct determination of the krypton separation yield. One cubic metre of air can be processed in about 4 h with 80 to 90% krypton recovery resulting in a 2-sigma error of the 85Kr concentration of less than 10%. The procedure is well suited to monitoring environmental air samples with respect to nuclear facilities, such as nuclear reactors and fuel reprocessing plants.