A new aerosol neutralizer was developed to charge submicron aerosols to the equilibrium charge distribution. Numerous advantages in comparison to known devices for neutralizing aerosols with corona discharge could be achieved by using an AC voltage and an optimized charger geometry. Extremely small particle losses, easy application, adjustment of charge input (ion concentration) and high aerosol throughput of the new charger make it ideal for replacing the widely used radioactive sources. The functionality of the new electrical neutralizer was tested for a pentaerythritol aerosol with low initial charge. Four different kinds of experiments were carried out, in order to obtain information about particle losses, overall charging efficiency, the fraction of uncharged particles and the ratio of negative to positive singly charged particles. Both the radioactive source (Model 3077, TSI Inc.) and the new charger gave the same results. Neutralization to the diffusion-based bipolar charge distribution was achieved for particle concentrations of 2.5 x 10(5)-4 x 10(6) cm(-3), with particle diameters ranging from 0.03 to 0.67 mum and volumetric flow rates between 0.3 and 0.75 l/min. (C) 2004 Elsevier Ltd. All rights reserved.