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 gm -3 reactor h -1, the weekly addition of MM from 6.8 to 13.6 mL MM L -1 vermiculite resulted in fluctuacting dynamics of ECs and spore emission. When varying the n-pentane IL from 25 to 875 gm -1 reactor h -1, a maximum EC of 110 gm -3 reactor h -1 associated with a spore emission of 1.8 × 10 4 CFU m -1 air was recorded. The critical inlet load for 90% n-pentane removal was 50 g m -3 reactorh -1 with spore emission 4.5 × 10 3 CFU m -3 air Finally, when the EBRT was decreased from 3.7 to 2.1 min at a constant n-pentane IL of 50 g m -3 reactorh -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 biomass g -1 vermiculite).