The operation of machine tools necessitates the protection of personnel from hazardous substances in the air and the prevention of damage to persons or building, especially through explosions. The guideline serves to provide manufacturers of machine tools, planners of extraction systems and the users or such system with recommendations for dimensioning and designing extraction devices for machines and the required filters. A method for determining the required extract air flows is specified. Economic aspects are taken into account, keeping air flows as small as possible so as to minimise the energy demand. Options for functional checking are given, extract-air cleaning techniques and the protection from fire and explosions are described.