This publication discloses an electrostatic filter construction, which includes electrodes connected to a first electrical potential, second electrodes, which are electrically insulated from the first electrodes, and an insulating material acting as a particle filter, which is located between the first and the second electrodes. According to the invention, in both of the electrodes the electrode material used is a material, such as activated carbon, which is permeable to a gas and which filters the gas, and which has a low electrical conductivity, and both electrodes are located essentially parallel to the direction of the airflow.