This research was conducted in an attempt to improve the work environment in livestock buildings. The overall aim was to develop and test a local ventilation system that will provide for more effective removal of air contaminants away from the worker's breathing zone. The effectiveness of conventional air inlets was first evaluated in a pilot-scale experimental facility. Three supply air inlets (one-way ceiling, two-way ceiling, and sidewall) were compared at three levels of ventilation rates in terms of relative ventilation effectiveness for airborne dust. The dust concentrations were measured with inhalable dust samplers, from which the relative ventilation effectiveness and the spatial variability in dust concentrations were obtained. General findings were as follows: 1. In general, ventilation rate or air exchange rate had limited effects on the relative ventilation effectiveness and spatial uniformity of dust concentrations. 2. The central alley had lower relative ventilation effectiveness than the pens for all three types of air inlets and for all ventilation rates. The pens receiving the fresh outside air first had the highest relative ventilation effectiveness. 3. The three air inlets differed in terms of ventilation effectiveness. The one-way ceiling inlet, in which the supply air jet was directed away from the exhaust fan, had the highest overall relative ventilation effectiveness, although it also had the highest spatial variability in dust concentration. The sidewall air inlet, on the other hand, had the most uniform dust concentration; however, it also had the lowest overall relative ventilation effectiveness. Various designs of local supply ventilation systems were then developed and evaluated in the experimental facility. The designs involved local supply ventilation in which fresh air was introduced down the central alley, representing the workers' breathing zone. Most of the designs resulted in low dust concentration or high relative ventilation effectiveness at the alley, although, in some designs, the dust concentration in one of the pens (representing the animal occupied zone) was extremely high indicating that little fresh air was being moved into that zone. The [mal design that was adopted and further evaluated in this research involved a perforated air inlet located near the center of the ceiling in 'combination with either the one-way or two-way conventional ceiling air inlet. This local supply ventilation system was designed expressly to introduce fresh air down the alley to the workers' breathing zone and reduce dust concentration in that zone. Comparing this system with the conventional air inlets illustrates the success of the local system in achieving that goal.