Ultrafine particles are known to be harmful to the human respiratory system. Therefore, measuring their UFP concentration is essential in research areas related to human health. Different technologies exist for measuring the concentration and size of particles. In the present study, an electrical aerosol detector was compared with two other particlemeasuring technologies, Scanning Mobility Particle Sizer spectrometer and Condensation Particle Counter. An electrical aerosol detector charges particles and later counts them according to their electrical movement. The particle counters were tested in a clean room with clean supply air. The results showed that the three
counters follow a similar pattern at a low level of particle concentrations. An exponential relationship was found between the electrical aerosol detector and the Scanning Mobility Particle Sizer spectrometer for high concentrations of particles. In the case of the existence of a corona discharge ionizer close to the measurement place, more evaluation is needed regarding the impact of it on the data of the EAD.