A customer of ours, who is active in the paint/coating industry, has a biofilter that doesn’t perform in an optimal way. In order to guarantee an optimal functioning of a biofilter, there are several parameters that must be taken into account, being pH, temperature, humidity. If these parameters are not within certain values, the biofilter will lose a large part of its efficiency. We then investigated why the biofilter was not functioning properly, based on a few samples. Based on a few samples and using analyses, we mapped the "health" of the biofilter. Finally, the observations are also immediately linked to measured emissions, so that we can continue to guarantee a good follow-up and see the effect of the expended efforts.