The behaviour of two biotrickling filters connected in serie (BTF) inoculated with Acidithiobacillus thiooxidans and Thiobacillus thioparus, biodegrading hydrogen sulphide (H 2 S) and dimethyl sulphide (DMS) simultaneously were studied. A model which considers gas to liquid mass transfer and biooxidation in the biofilm attached to the support is developed. Additionally, a fixed bed biotrickling filter where the microorganism is immobilized in a biofilm which degrades a mixture of H 2 S and DMS is implemented. Validation of the model was carried out using experimental data obtained at different H 2 S and DMS loads. Results: The inhibitory effect caused by the presence of H 2 S on the DMS is observed, which is evidenced by the decrease of the DMS removal efficiency from 80 to 27%, due to the preference that T. thioparus has by simple metabolism. H 2 S is not affected by the DMS, with removal efficiencies of 95 to 97%, but it decreases at high concentrations of the compound, due to the inhibition of metabolism by high H 2 S input loads. The model which describes the BFT fits successfully with the experimental results and it has a high sensitivity to inhibition parameters. Conclusions: It is shown that the microorganism has a high affinity for H 2 S, producing substrate inhibition when the concentration is high. The H 2 S is able to inhibit the DMS biooxidation, whereas the DMS does not affect the H 2 S biooxidation.