Our standard bars for working distances of about 50 mm on average in ranges from 20 to 400 mm, without air.
If ionizers can be mounted close to the material, i.e. in the range between 20 and 150mm distance to the material, even with high material charges usually high voltage of > 12kV is not necessary. In the case of Longrange Bars this is only needed in order to overcome the distances. The electric field must be maintained there over a long distance, which is not necessary at close distances.