In the present work, surface turbulence characteristics at the onset of entrainment in air water system have been investigated. For the present study, shear type entrainment in stirred tanks has been considered. Experiments have been performed in stirred tanks with different scales for different types and sizes of impellers. The results of the work reveal that radial RMS, axial RMS velocities and turbulent kinetic energy showed similar magnitudes at onset even at different scales. The RMS velocities as well as TKE magnitudes did not vary with type or size of impellers. Local energy dissipation rates have been estimated from autocorrelation function of fluctuating velocity. Very low magnitudes of local energy dissipation rates at onset have been observed. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.