Biofiltration is a simple, effective, economically viable and the most widely used gas treatment technique for treating malodors at low concentrations and high flow rates. This paper reports the performance of two lab scale immobilized cell biofilters operated in continuous mode for hydrogen sulfide ($H_2S$) and ammonia ($NH_3$) removal. The removal efficiency (RE, %) and the elimination capacity (EC, $g/m^3{cdot}hr$) profiles were monitored by subjecting the biofilters to different loading rates of $H_2S$ (0.3 to $8;g/m^3{cdot}hr$) and $NH_3$ (0.3 to $4.5;g/m^3{cdot}hr$). The removal efficiencies were greater than 99% when inlet loading rate to the biofilters were upto $6;gH_2S/m^3{cdot}hr$ and $4;gNH_3/m^3{cdot}hr$ respectively. The performance of the biofilters were also ascertained by conducting shock loading studies at a loading rate of $10;gH_2S/m^3{cdot}hr$ and $6;gNH_3/m^3{cdot}hr$. The results from this study show high removal efficiency, good recuperating potential and stability of the immobilized microbial consortia to transient shock loads.