This study evaluated the performance of a lab-scale, closed bed biofilter for the removal of odour in off-gas released from an industrial fermentation facility. This off-gas was emitted from the facility periodically after the sterilization of fermentation medium. The lab scale biofilter was operated for over two months, totalling 30 medium sterilizations. The biofilter was subjected to a shock odour load for each sterilization cycle and to two airflow conditions: the fermentation off-gas and compressed room air, which was cooler and drier than the fermentation off-gas. The biofilter was effective in removing odour under shock loading and variable operating conditions (temperature and relative humidity). An odour reduction rate of 72% was achieved immediately after medium sterilization when odour levels were highest (32 800 OU m(-3)). The filter had an odour removal efficiency of 61% and 67% for 24 h and 50 h after sterilization, respectively.