Written by Casey Zangaro under the direction and review of Joe Darrington (former SDSU Extension Livestock Environment Associate).
Understanding Air Infiltration
Air infiltration in large, confined swine operations has been an on-going problem for producers for many years. Regardless of technological advancements in building design and construction, unwanted air penetration continues to be a consistent problem. Influx of unregulated air into the barn causes both health and economical concerns due to inconsistent air quality and temperature management. Therefore, understanding and initiating management practices that limit the entrance of unregulated air into an operation will drastically benefit swine operations.
Air infiltration is a primary concern for producers because of the impact on barn efficiency. Producers invest in facilities with the expectation that they contain proper ventilation and management protocols to assist in raising a healthy herd. However, the management of air infiltration requires a thorough understanding of the environment. For example, during the summer, warm air can come in through unwanted areas which can lead to pigs overheating and high-staged fans overworking. Conversely, in winter months, cold dry air leaks through the cracks and doors of the barn where it influences certain pens and increases the requirement for the barn heater to run longer. Air infiltration can also lead to disease transmission if multiple swine barns are located in close proximity to each other.
Air infiltration can be classified into a few categories expressly found within swine barns across the country.
Interflow is commonly overlooked by barn management because it is air that has leaked from one internal room to next, specifically to one with housed animals. For example, air travelling from the shower rooms and/or offices into the main animal area. Interflow is not a major concern for spreading disease. However, subtle air changes in the barn can make a drastic difference in overall barn ventilation and system operation.
Inflow is identified as air that leaks from an external environment, via fans or doors, and mixes with the air inside the animal unit. This is a concern for a couple reasons, namely possible disease transfer and increased potential for drafts during winter months.
Short-circuiting is identified as outside air coming into the barn but not mixing appropriately with indoor air. This creates a major ventilation inefficiency within the barn; because as the outside air “sticks” to the end of the pens that are near the fans, the air in the pig space is vastly different than the front of the pen. It also has the potential to alter temperature and humidity intermittently throughout the barn depending on the leak’s location. These different air infiltration categories all lead to changes in the barn’s static pressure.
Figure 1. Thermal image of infiltration around curtain under grommet attachment (left) and around door and through single-layer shutters (right). Images captured with FLIR E6.
Ventilation systems create ideal static pressure within a barn by balancing fan operation with appropriate inlet openings. Simply said, fans are used to create a vacuum-effect within a negative pressure swine facility by exhausting air. The static pressure of a swine facility should optimally be between 0.4 to 0.6 inches of water. However, this is difficult to maintain if any of the three air infiltration categories are leaking air into the facility. For example, any unplanned openings will affect air distribution throughout the barn, which will result in a reduced static pressure. This lack of controlled static pressure will lead to drafts or humid areas inside the barn depending on the season. These issues could result in reduced health in younger pigs who struggle to maintain body temperature. Ultimately, these health concerns only reinforce the necessity for air infiltration solutions.
Influencing air infiltration does not have to be a complicated endeavor. It can be as simple knowing where the air is coming into the barn and keeping up with regular annual maintenance. Barn fans and inlets should be checked regularly throughout the year to prevent breakdown or any inefficiency. If a barn is utilizing curtains, any holes or gaps will need to be fixed to prevent air leaks. Thus, patching, or even replacing, the curtains will benefit the ventilation system tremendously by eliminating air infiltration sites. Furthermore, limiting prolonged opening of doors can reduce both interflow and inflow air infiltration.
Air infiltration, or the inlet of unwanted air into a ventilated facility, can seriously impact production and herd health. It is important to be aware of any potential air infiltration locations and to manage them appropriately. Air infiltration can cause ventilation systems to become less efficient, decrease animal well-being, and potentially increase the likelihood of disease transmission between facilities. However, simple steps can be taken to decrease the effect of air infiltration on the pigs and their housing environment.
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