Abstract: An electrical ionizer comprising a fan (5) for producing a laminar flow of air; a positive ion emitter (6b) for ejecting positive ions into the flow of air; a negative ion emitter (6a) for ejecting negative ions into the flow of air; a positive voltage supply (27) to the positive ion emitter; a negative voltage supply (28) to the negative ion emitter; and a microprocessor (30) for controlling the positive and negative voltages to obtain a desired ion balance in the flow of air. The fan (5) is a crossflow fan, resulting in a highly uniform and laminar beam of air along the entire length of the fan, with reduced gaps in the air flow and consistent velocity of air, improving ion balance.