An importance safety consideration when designing laboratory exhaust systems is the exhaust fan’s stack height and exhaust stack height. Air intakes on the same building and even adjacent buildings need to be considered so that no contaminated exhaust in re-entrained into any building supply air. To properly design a system for operation and safety, the engineer needs to know the discharge volume and dilution percentage to avoid re-entrainment of concentrated and hazardous exhaust.
Specially designed laboratory exhaust fans called High Plume Dilution Laboratory Exhaust System – YFLES (induced air fan) have a feature where additional outside air is entrained by the fan into the exhaust air stream, mixed and sent high into the wind. But how is this additional induced air determined so that the engineer can be assured of getting the accurate information?
Fan manufacturers working in conjunction with AMCA have developed a two-test process for measuring and certifying the total exhaust volume. Initially, the induced air fan is installed in an AMCA 210 Figure 15 configuration. In this configuration, the fan’s inlet air performance is measured at different static pressures, utilizing an air measurement chamber. This provides information on what air volume is passing through the fan’s air inlet. This is the first step of what is needed to determine the performance of an induced air fan.