Effects of sash movement and walk-bys on aerodynamics and contaminant leakage of laboratory fume cupboards.

In order to speculate the physical mechanisms of contaminant leakage during sash movement and walk-bys through a laboratory fume cupboard, the complicated three-dimensional flow patterns and the real-time tracer gas leakage are studied via the laser-assisted flow visualization method and the standard gas sampling technique, respectively, over a transparent, full scale chemical fume cupboard. Through the flow visualization, the evolution of drastic changes of the flow pattern is demonstrated. The highly turbulent jet-like currents are induced by the unsteady flow motion near the cupboard face. Large-scale turbulent eddies accompanied with the jet-like currents obviously bring large amount of in-cupboard smoke out to the atmosphere. The turbulent mixing extends the size and the strength of the large-scale eddy circulations, and predominantly contributes to the mechanism that causes the severe spread of contaminant leakage in few seconds. The tracer gas tests that are conducted by employing pr-EN 14175:2003 method show consistent containment results with the flow visualization findings. The temporally evolving large-scale turbulent eddies induced by the sash movement and the walk-bys cause substantially high contaminant leakage to the environment and the breathing zone of the operator.