The environmental impact and potential public health impacts of naturally ventilated pig barns with outdoor exercise yards are less well studied compared to conventional intensive housing systems. The aim of this paper was to investigate the characteristics of airflow and gaseous emissions from an outdoor exercise yard in a naturally ventilated pig barn, and the impact of the barn emissions on the surrounding environment. The investigations were carried out using a 1:50 scaled pig barn model with different inlet opening sizes and roof structures in a large atmospheric boundary layer wind tunnel. Air velocities at the emission active surface, as well as air velocities and tracer gas concentrations at four planes downwind of the barn model were measured using a 2-dimensional Laser Doppler Anemometer and a Fast Response Flame Ionisation Detector system. It was found that the opening size and roof structure had a large impact on the airflow patterns and thus on the gas dispersion. The airflow measurement results demonstrated that the pig barn with small openings especially those without roof over the outdoor yard might have less environmental impact on the surroundings. This study contributed to a detailed understanding of airflow and dispersion characteristics downwind the pig barn and provided insights for structural design of similar pig barns aiming to mitigate their environmental impacts.
