The ready-dosed salt packages available from Vaisala are delivered with calibration certificates given on the basis of a batch check. In other words, a sample of packages is taken from a batch and salts are prepared according to the instructions given in this manual. These salt solutions are then checked at the Vaisala Measurement Standards Laboratory (a calibration laboratory accredited by FINAS, a member of the European Cooperation for Accreditation of Laboratories). The calibration certificate certifies that the equilibrium humidities generated by these salt solutions correspond to Greenspan's calibration table within the specified accuracy.