The functional principal of biofilters was recognized and used back in the 1920’s to clean contaminated exhaust gas. It was first invented for use in waste water treatment facilities in Germany, by a scientist named H. Bach. Over the past century, the technical implementation has been optimized for a multitude of uses. A biofilter is a simple and cost-effective way to clean odorous exhaust gas. It consists of a container with wood chips as the substrate. As hot gas leaves the dryer, it cools and water from it condenses in the biofilter on the substrate, making the perfect living conditions for microorganisms. They break down harmful substances that become trapped in the condensed water from the exhaust gas and neutralize any odors, expelling carbon dioxide. Odorous substances are almost completely oxidized as a result. Biofilters are rarely needed to treat the air discharged from our dryers but are a simple and cost-effective solution when needed.