Gas phase biofilters are a proven method for reducing odor and other gaseous emissions from swine facilities. The purpose of this project was to evaluate six biofilter media. The media were: wood mulch, lava rock, cedar chips, pine bark nuggets, western pine bark and wood shreds. Media sieve analysis, porosity and unit pressure drop versus unit airflow relations were determined. In phase 1 media reduction efficiency and pressure drop were measured in a biofilter media testing unit with six columns with individually controlled airflow rates and moisture control. Reduction efficiency was evaluated based on total reduced sulfur and ammonia (NH3) removal. In phase 2, three media, wood shreds, pine bark nuggets and lava rock were placed in duplicate columns and evaluated for pressure drop and total reduce sulfur and NH3 reduction efficiency. In phase 3, pine bark nuggets were used in all six columns with two empty bed contact times (EBCT) (i.e., 1 s and 5 s). The percent total reduced sulfur, NH3 and odor reduction efficiency were evaluated. Pine bark nuggets and lava rock had the lowest unit pressure drops versus unit airflow rates. In phase 1, all of six media were effective after seeding. Reduction efficiency for total reduce sulfur was between 21 and 75% and between 43 to 80% for NH3. In phase 2, all three media performed well using an average EBCT of 5 s. In phase 3, the biofilters with 1 s EBCT had lower percent total reduced sulfur, NH3 and odor reduction efficiency than biofilters with 5 s EBCT.