BACKGROUND: The effect of the inlet n-pentane load (IL), empty bed residence time (EBRT) and mineral medium (MM) addition on spore emission and elimination capacity (EC) was evaluated using the fungus Fusarium solani in a vermiculite-based biofilter. RESULTS: When the process was operated at an EBRT of 3.7 min and an IL of 100 g m(reactor)(-3) h(-1), the weekly addition of MM from 6.8 to 13.6 mLMM L(vermiculite)(-1)resulted in fluctuacting dynamics of ECs and spore emission. When varying the n-pentane IL from 25 to 875 g m(reactor)(-3) h(-1), a maximum EC of 110 g m(reactor)(-3) h(-1) associated with a spore emission of 1.8 x 104 CFU m(air)(-3) was recorded. The critical inlet load for 90% n-pentane removal was 50 g m(reactor)(-3) h(-1) with spore emission 4.5 x 103 CFU m(air)(-3). Finally, when the EBRT was decreased from 3.7 to 2.1 min at a constant n-pentane IL of 50 g m(reactor)(-3) h(-1) the EC decreased by 110%. CONCLUSIONS: The results show a poor performance of the n-pentane biofiltration system at high IL and low EBRT, which was further confirmed by the low final biomass concentrations in the biofilter (62 mg(biomass) g(vermiculite)(-1)). Copyright (c) 2012 Society of Chemical Industry