Air flow

Thermal images of infiltration around curtain under grommet attachment (left) and around door and through single-layer shutters (right). Images captured with FLIR E6.

Editor’s note: The following was written by Ryan Samuel, Xufei Yang, Casey Zangaro and Joe Darrington with South Dakota State University for the university’s website.

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.

Air infiltration can be classified into a few categories expressly found within swine barns across the country:

=Interflow: 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 traveling 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.

=Inflow: 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: 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 the outside air “sticks” to the end of the pens that are near the fans. The air from the pigs 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.

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. 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.