The formation of primary particles in the welding fume with regard to gas phase ionization is studied. It is shown that the classical theory is applicable only to the initial moment of condensation of the metals' vapors. The fast coagulation of nuclei leads to the formation of droplets which can unrestrictedly grow and get charged. The subsequent nucleation and growth of the primary particles take place in the charged gas environment with the intensive interphase exchange of the charges and energy. It is shown that the increase of the coagulated droplets' charge leads to the shift of the nucleation in the high-temperature range and to the increase of the primary particles sizes. (C) 2012 Elsevier Ltd. All rights reserved.