Mycoplasma hyopneumoniae is known to enhance the effects of the PRRS virus. By infecting a pig herd with epidemic levels of PRRS and M hyo, this study wanted to find out the meteorological factors that increases the spreading of PRRS and the efficiency of different air filters. Three sites that were close together were used: one infected with the PRRS virus and M hyo and two others ,the first with good filtration and the second with little to no filtration. This study did assessments based on quality of air samples taken over a two year period, and changing weather patterns. The study was still being conducted but has found that PRRS had been transported into the no filtration system but not the highly filtrated system. Assessing data of weather patterns found that PRRS in the air was more common on cloudy days, with low temperatures and high humidity levels. This suggests that weather plays a factor in the spreading of the PRRS virus.