Worker Exposure due to Reverse Flow in Push‐pull Ventilation and Development of a Reverse Flow Preventing System

Worker Exposure due to Reverse Flow in Push‐pull Ventilation and Development of a Reverse Flow Preventing System: Jun O jima , National Institute of Industrial Health —An experimental mock‐up push‐pull ventilation system was constructed in a laboratory and a dummy worker was placed in its ventilation area (uniform flow field). Within the uniform flow field, organic solvent work was modeled by setting up an alcohol vapor generator and a working table in front of the dummy worker. Reverse flow was observed in the breathing zone of the dummy worker when it was positioned in the uniform flow originating from behind the worker. The experiments showed that reverse flow increased the worker's contaminant exposure significantly. With the 1.0 m/s uniform flow originating from behind the worker, the alcohol concentration in the breathing zone exceeded 300 ppm due to the reverse flow, but it was too low to be detectable when the worker's orientation relative to the uniform flow was 90 degree. In order to control the reverse flow and minimize the contaminant exposure, the author invented a prototype of a reverse flow preventing system. The reverse flow preventing system reported in this study was designed to be set up in a position between the worker and the working table. It decreased exposure by means of locally supplied air blowing which blocked the reverse flow and contaminant transportation from the source.