Curtain sided deep-pit swine finishing buildings are popular in the industry due to concerns related to odors from outdoor manure storage systems. Local regulators are requesting additional odor reduction from the building. Biofiltration is a technology that reduces odors exhausted from swine buildings if the exhaust air can be controlled. Upward air movement through the slatted floor must be eliminated to treat all pit gasses when the ventilation is operating in a mode with the curtains lowered.

Critical (minimal) pit ventilation rates were determined to insure downward air flow through the slatted floor in a swine finishing barn with 8, 11, 14, 17, 20, 23, and 36 percent floor opening. The critical air velocity through the slatted floor averaged 36.2 ft/min (SD = 1.2 ft/min).

Using a safety factor of 1.5, the design criterion is 50 cfm/pig for pit ventilation rate before the curtains are lowered for full-slatted barns to assure no upward air movement from the pit after the curtains are lowered. This recommendation will provide continuous biofilter treatment of pit gasses for all ventilation modes.