Fume Hood Performance: Using a Bypass in Variable Air Volume Systems

Abstract

Abstract Variable air volume (VAV) exhaust systems provide sophisticated engineering controls for maintaining laboratory ventilation. Depending on how they are installed, they may be very responsive to changes in air flows and air pressures. Some of these changes are a consequence of natural phenomena and some are induced by the transit and actions of laboratory occupants. While the responsiveness of VAV controls can provide tight regulation, the dynamic nature of the VAV system may also introduce undesirable air flow fluctuations. Further-more, since the volumes of air being exhausted vary, the amount of air available for fume hood capture and containment will also vary. These studies examine the responsiveness and consequences of ventilation system perturbations, as well as the effect of fume hood exhaust being reduced to very low air volumes. Face velocity and air volumes were measured at different sash heights and in response to rapid sash movements. In addition, capture of contaminants was evaluated ...