The effect of relative humidity (RH: 30% to >95%) of a gas-phase mixture composed of benzene, toluene, ethylbenzene and para-, meta- and ortho-xylenes (BTEX), inlet concentrations (0.2-12.6 g m(-3)), and empty bed residence times (EBRTs) (48-144 s) was tested in a fungi-dominant biofilter. A maximum elimination capacity (ECmax) of 244.2 gBTEX m(-3) h(-1) was achieved at a total inlet loading rate (ILRT) of 371.2 gBTEX m(-3) h(-1) (RH: 65%). The transient-state response was tested by increasing the ILRT, in two steps, from similar to 50 to 850 g m(-3) h(-1) and from similar to 50 to 320 g m(-3) h(-1), at a constant EBRT of 41.7 S. Increasing the ILRT reduced the total BTEX removal efficiency (RET) from >97% to 35%, and from >90% to 60% during medium and high shock-load, respectively. When subjected to short (4 d) and long-term (7 d) shut-down periods, the biofilter was able to recover high ECmax of, respectively, 200 and 72 gBTEX m(-3) h(-1) after resuming operation. (C) 2012 Elsevier Ltd. All rights reserved.