Swine producers are exposed to dusts and gases when working in barns. Previous studies have shown that people who work in swine barns are at a greater risk of developing respiratory symptoms, decreases in lung function levels and increases in airway reactions. One method of reducing exposure to dust is by wearing a disposable respirator (mask) during barn work activities. This study compared subjects who spent 4 hour time periods in a barn wearing a mask to those who were not wearing masks. On average, a reduction in lung function of 8.12% was observed over a 4 hour period. Similar trends were seen in other measures of health status. It was concluded that a well-fitted disposable mask over the 4 hour period by persons previously unexposed to swine barn environment reduces respiratory symptoms and reductions in lung function. However, exposure to barn environment long term requires development of production and engineering control technologies to allow workers a healthful environment.