Preparation of calibration gas mixtures for the measurement of breath alcohol concentration

Calibration gas mixtures for breath alcohol measuring techniques need to have a defined ethanol concentration in water-saturated air. For the calibration of evidential breath analysers in Germany, these gases are prepared at the Physikalisch-Technische Bundesanstalt according to the saturation method. The ethanol concentration is calculated via the air-liquid partition ratios of the air-water-ethanol substance system. This article deals with the selection and critical consideration of different preparation methods for test gases and their applicability to the specific gas mixture required for breath alcohol measurements.