Biofiltration is an efficient, easy and cost effective, environmental friendly process for treating of ammonia from air. The aim of this study is a comparative study of ammonia removal from air by biofilters with porous compost and processed soil. In order to remove ammonia, two columns with 14 cm inner diameter were used. One of the columns is filled with porous compost and another column is filled with processed soil and scallop (scallop: processed soil, 1:4). The performances of biofilters were studied under 10 different flow rates (1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 lit/min) and 5 different NH3 concentrations intervals (0-20, 20-40, 40-60, 60-80 and 80-100 ppm) in the 25 degree Celsius temperature and optimum moisture (40-80%) interval. The results of this study show that efficiency is decreased when flow rate or concentration is increased. The efficiency of porous compost was changed between 84.6 - 98.2% and the efficiency of processed soil was changed between 91.5 – 100%. Maximum efficiency for both of the beds occurred on 0.19 g/(m3.h) loading rate. Efficiency of processed soil and porous compost was in 0-20 concentrations intervals at 1 lit/min flow rate and beds attained 240 seconds. According to the results, for ammonia removal, the processed soil bed is more efficient than the porous compost bed.