A strategy for providing partial biofiltration of a critical minimum amount of ventilation air (CMVR) from a hybrid ventilated swine finishing facility was developed and tested. The CMVR, defined as the minimum treated exhaust air that suppressed nighttime curtain opening movement, was set at 81 m3 h-1 pig-1 with the intention of providing enough fan ventilation to suppress inlet curtain movement during stable atmospheres, providing biofiltering for a high percentage of exhaust air. Two side-by-side 300-head hybrid ventilated deep-pit swine finishing rooms were used for this research, one room as the control (CTL) with the other treatment (TRT). The TRT room was fitted with a wood-chip based biofilter for scrubbing the CMVR. In terms of total room emissions, the TRT room had an average odor emission 37% less than the CTL room. Ammonia emission was 58% lower for the TRT room as compared to the CTL room. The results presented indicate that a strategy of partial biofiltration can result in significant reductions in odor and ammonia emissions when applied to hybrid ventilated swine finishing barns.