Industrial emissions are main source of pollution.Monitoring of emissions of organic compounds and heavy metals contribute to the improvement of environmental protection and the exact analytical results can allow you to monitor the development of existing and potential pollution.The use of certified reference materials(CRM)enables the verification of the correctness of the results.In 2012 started the implementation of tasks within the project MODAS.Final results of this work will be obtain a "package" six certified reference materials,which can be regarded as a response to the needs of Polish analytical laboratories in the field of broader environmental analysis.Four of them(bottom sediment,herring tissue,codfish tissue,cormorant tissue)select characteristic for trophic chain of Polish marine ecosystem.These materials will be characterized by both the diversity of the composition of the matrix as well as a wide range of analytes.The most important feature of the production is to be representative of the composition of both the matrix and the levels of analytes in comparison to typical environmental samples tested in the Polish analytical laboratories.Tests of homogeneity are essential feature for the certification of reference materials and should demonstrate the importance of certified values and their uncertainties in the analysis of individual units.Particular care should be taken during preparing for the creation of a homogeneous material.In this work,a general scheme of the procedure in the conduct of homogeneity testing of metals in the above-mentioned materials.