An ionization air purification system for the passenger cabin of vehicles, which modifies the degree of ionization by modifying the energy levels applied to an air ionization device having a tubular dielectric member or a planar dielectric member or ionization source proportional to the change in air flow dynamics and air quality. In one embodiment, an ionization air purification system for the passenger cabin of a vehicle is disclosed. The system includes an ionization device for purifying the air prior to entering into the passenger cabin of the vehicle while minimizing the production of ozone as a by-product; and means for modifying the degree of ionization by modifying the energy levels applied to the ionization tube or ionization source proportional to the change in air flow dynamics or air quality.