A mobile pilot-scale biofilter testing laboratory, which consisted of one- and two-stage biofilter reactor barrels, was developed where two types of wood chips (western cedar and hard wood) were examined to treat odor emissions from a deep-pit swine finishing facility in central Iowa. The biofilters were operated continuously from July 20 to October 17, 2007 at differe nt air flow rates resulting in variable empty bed residence times. During this test period, solid-phase microextraction 85 µm Carboxen/PDMS fibers were used to extract volatile organic compounds (VOCs) from both the control plenum and biofilter treatment. Analyses of VOCs were carried out using a multidimensional gas chromatography-mass spectrometry-olfactometry system. Reductions of nine odorous compounds were reported. An overall average reduction efficiency of 98.9% and 96.4% was achieved for two-stage western cedar and hardwood biofilters, respectively. The results showed that maintaining proper moisture content is critical to the success of wood chip-based biofilter.