From monitoring mechanical waste treatment on landfill sites in Hattorf and Blankenhagen the subproject exhaust air analysis of compost windrows using the reduction cover system helsasorb eco has emerged. The manufacturer Helsatech (Helsa Group) does not offer precise information regarding emission reduction performance. Hence the effect of the reduction cover system has to be investigated. Therefore comparative emission measurements with and without the cover system have to be done to evaluate the efficiency.