It has been proven and repeated that the PRRS virus can travel by air and this is being associated with PRRS outbreaks in negative herds. This has lead to a need for a better understanding of air filtration as the practice is being adopted by many facilities. Installing filters can be a large task requiring many filters and time to install them and change them with the season, but an alternative can be air conditioning which cools air year round making summer and winter filtration basically the same. Some barns who are using various styles of air conditioners include a recirculated air system which cycles air in the barn through the air conditioner, others uses various styles of fresh air systems, where air enters through the roof or through the side of the barn and shut off and turn on based on changing temperatures. Because air entering the barn is regulated and consistent year round one filtration system is required for winter and summer. The costs of putting in an air conditioning system range from around $300-600 dollars per pig. Most of these costs are associated with installation and renovation, the electrical set up on the farm, the type of air conditioner (recirculation is cheaper but requires more maintenance) as well as other factors. The cost of air conditioning is expensive but has potential to reduce the costs of purchasing and installing filters year round. Also with less air entering the facility the chances of PRRS infecting a herd may go down.