The innovative local ventilation systems using vortex flows resembling a tornado have been proposed to improve ventilation performance. The effect of two primary operating conditions, the side jet velocity and exhaust flow rate which are essential for the formation of vortex structures and significantly affect the resulting vortex characteristics, on the vortex characteristics are investigated by employing a particle image velocimetry (PIV) technique. The vortex core is widened and the vortex strength increased when the side jet velocity is increased. When the induced swirling force is sufficient, a higher exhaust flow rate can form a stronger and more stable vortex. Vortex characteristics revealed that the optimal side jet velocity is 1.73 m/s corresponding Res of 2332.4 with a normalized exhaust flow rate of 0.155. In order to quantify the effectiveness of the vortex ventilation system, the concentration of ultra-fine particulate matters was monitored. The ventilation performance has a similar trend with vortex size, circulation and swirl ratio over core region. We herein propose a new-type ventilation system and a useful analysis method based on PIV to characterize tornado-like flows in vortex ventilation systems. In addition, these flow and ventilation results can be used as basic data in the design and operation of vortex ventilation systems.