The ppc biofilter provides a quality pretreatment system to condition the gas stream for optimum biological parameters. This includes temperature control, humidification and particulate removal. The gas stream then flows into a fixed ppc biofilter reactor where the phase transfer and biological oxidation takes place. The polluted air stream is humidified before entering the biological reactor. The environmental pollutants then contact with the ppc biofilter systems where they transfer from the air phase to the water phase. The water phase is represented by a thin biological film surrounding each particle. Here, the bacteria produce an enzyme which acts as a catalyst, breaking the chemical pollutants down with the final emissions of carbon dioxide and water.