Biofiltration of Triethylamine (TEA) vapor used as a catalyst in casting operations was evaluated in this study. The unit consisted of a 6-L three-stage biofilter containing a mixture of compost and wood chips (40:60 v/v) as the filter medium. Seed microbial population from municipal activated sludge was acclimated for a period of three weeks prior to the actual experimental runs. In the startup period, high pH values up to 10 was observed due to alkaline nature of TEA and inadequate formation of biofilm and low overall biodegradation. Steady increase of organic-N concentration along with gradual upward trend of pressure drop indicated sound establishment of microbial population. Operational parameters studied included loading rate (6-116 g/m3/h), hydraulic detention times (40-60 s), temperature ( 30Â±1Â°C), and humidity (50-55%). Results indicated effluent ammonia concentrations meeting standards of 25 ppm can be obtained after 2.5 months of operation. Optimal organic loading rates (OLRs) of 90Â±14 g/m3/h for Hydraulic Retention Time (HRT) value of 48 s were suggested. Under these conditions, elimination capacity of 71Â±3 g/m3/h and removal efficiency 81Â±14 % were achieved. Mass balance was performed on different forms of nitrogen products for a constant inlet concentration of 180 ppm TEA with a relatively stable removal efficiency of about 90 % maintained for over a month. Both liquid (leachate) and gas (different sections, inlet, and outlet) phase measurements were made for the purpose of performing calculations. Ammonium-N and Nitrate-N were dominant in the first and third sections of the reactor, respectively. Cumulative TEA-N mass balance over a 2-month period indicated an equal proportion breakdown into ammonia-N, nitrate-N, and ammonium & organic-N. The fact that up to 30 % of TEA-N could not be accounted for in the leachate and gas measurements can be attributed to incorporation into the cellular constituents.