The objective of this on-site experiment was to evaluate and compare the effectiveness of currently utilized various additives, i.e. tap water, salt water, digested manure, microbial additive, soybean oil, artificial spice and essential oil, to reduce odor emissions from the confinement pig building. Odor reduction rates were evaluated with respect to sensual odor (odor concentration index, odor intensity and odor offensiveness) and odorous compounds (ammonia and sulfuric odorous compounds). Of the additives investigated in this study, salt water, artificial spice and essential oil had a positive effect on reducing odor generation. The effectiveness of salt water was only observed on ammonia, showing the reduction rates as a function of time (t=immediately, 1h, 3h, 5h, and 24h after spraying) were 0.1%, 20%, 36%, 11% and 0.2% as compared to initial level before spraying. The odor intensity and offensiveness were lessened by spraying artificial spice and essential oil of which maximum reduction rates ranged from 60% to 80%. Additionally, the essential oil had a significant effect on reducing sulfuric odorous compounds for 24h after spraying, which implicates that it functioned as not only a masking agent but also as an antimicrobial agent.