The BElectrostatic aerosol Neutraliser EAN 581 from Topas conditions the charge distribution of test dusts and other aerosols, like required in ISO 11155-1 and DIN 71460-1. Charge equilibrium can be controlled by mixing positive and negative ions in a precise manner. The mechanical interaction of particles, especially solid ones, may cause undesirable levels of electrostatic charge. Test dusts must be generated with a high degree of reproducibility for instance when evaluating aerosol separation techniques such as cyclones, filters or impactors. Comparable results can only be obtained at controlled and similar charge levels.