Materials that are used outdoors can be preserved by biocides to prevent disturbance by organisms, mainly colonisation by microorganisms. These applications may cause emissions of active substances into environmental compartments via leaching processes. The European Biocidal Products Directive 98/8/EC (BPD) requires an assessment of environmental risks caused by the use of biocidal products. This report describes methods for characterisation of leaching of biocidal active substances from different materials under weathering conditions. Biocidal products used to preserve materials belong to main group  2 ‘preservatives’.