Ventilation efficiencies of desk-mounted task/ambient conditioning systems

In laboratory experiments, we investigated two task/ambient conditioning sy stems with air supplied from desk-mounted air outlets to efficiently ventil ate the breathing zone of heated manikins seated at desks. In most experime nts, the task conditioning systems provided outside air while a conventiona l ventilation system provided additional space cooling but no outside air. Air change effectiveness (i.e., exhaust air age divided by age of air at th e manikin's face) was measured with a tracer gas step-up procedure. Other t racer gases simulated the release of pollutants from nearby occupants and f rom the floor covering, and the associated pollutant removal efficiencies ( i.e., exhaust air concentrations divided by concentrations at manikin's fac e) were calculated. High values of air change effectiveness (similar to 1.3 to 1.9) and high values of pollutant removal efficiency (similar to 1.2 to 1.6) were measured when these task conditioning systems supplied 100% outd oor air at a flow rate of 7 to 9 L s(-1) per occupant. Air change effective ness was reasonably well correlated with the pollutant removal efficiency. Overall, the experimental data suggest that these task/ambient conditioning systems can be used to improve ventilation and air quality or to save ener gy while maintaining a typical level of IAQ at the breathing zone.