The OECD is inviting interested labs to participate in a round-robin exercise (HARN exercise) in the context of its ongoing project on Testing Guideline on determination of the dustiness of manufactured nanomaterials, led by Denmark and France. The goal of the exercise is to assess the robustness, feasibility, and appropriateness of different dustiness methods for the testing of HARN,and the morphological characterization and analysis using electron microscopy. Further details on how to apply, and on the intra‐ and inter‐laboratory comparison test, can be found in the attached document. The deadline for responses is March 31st.