With the aim of reducing formaldehyde emissions for the end user of wood products, the wood industry is striving to reduces these emissions with the help of several factors. One of the factor with which can affect formaldehyde emissions, is the means of treating surfaces, with sanding being part of this. In the diploma thesis we used a study to determine how sanding and the roughness of the sandpaper affect formaldehyde emissions. In the study we sanded eight test pieces of chipboard and eight test pieces of fibreboard (both glued with urea-formaldehyde glue), sanded them using sandpaper of various grit size (40, 80 and 120), and then used a gas analysis method to measure the formaldehyde emissions of the individual test pieces. We found that the most formaldehyde was released from sanding with sandpaper of a smaller grit size. This means that if you want to remove as much formaldehyde as possible during the actual production process of chipboard and fibreboard, sandpaper with the smallest possible grit size should be used, while if you want to achieve the opposite (to limit formaldehyde emissions during the process as much as possible), sandpaper with as large grit size as possible should be used.