A new, simple and fast method for calibration of water-absorbing method for measuring mass concentration of PreAerosol Compounds (PreAC) in atmospheric air is developed. The method is realized in a generator of a given concentration of low-volatile vapors of a wide class of substances. The principle of generation is based on insertion of a known amount of the substance saturated vapor into the studied airflow. As is shown by means of the generator, the uncertainty of the vapor content measured by the water-absorbing method is less than 10% in the mass concentrations range from 10 up to 3000 ng/m3. Applicability of the generator as a thermal-condensation source of aerosol nanoparticles is shown.