Org. beds consisting of compost soil (40%), peat (40%) and straw (20%) or oak chips (10%) and crushed bark (10%) were used for removal of org. impurities from piggery (650 pigs) exhaust air by biofiltration for 18 weeks. The air was forced with a fan (800 m(3)/h) and analyzed by gas chromatog. for 22 volatile org. compds. The beds contained mainly mesophilic and psychrophilic bacteria. NeH was the main impurity of the air (ca. 0.22 mg/m(3)). its removal degree by biofiltration was 86-89%. The removal of cyclobutanol, PrOH and indoles was also remarkable. The increase in concn. of I-PrOH and PHNe on both beds after biofiltration was rather peculiar.