Contents of volatile org. compds. in untreated air (inlet to waste treatment plant) as well as after filtration on a bed (mixt. of oak chips, biomass and shredded bark) at air temps. from - 2 degrees C to 27 degrees C, bed temps. 10-21 degrees C, bed humidity 75.1-88.8% and pH 4.4-6.7 were detd. chromatog. in accordance with the relevant stds. The results were used to det. effectiveness of air deodorization. The pH of the bed had the highest impact on the cleaning efficiency.