preferably the outer casings of the cvd reactors the pipelines and the floors of the production rooms are cleaned at least once per week however particular preference is given to cleaning the floor of a production hall at least two times per week and to clean the pipelines and the outer casings of the reactors at least once per day it has been found that such a type of cleaning is so efficient that the installation of expensive clean room technology is superfluous as a result considerable capital costs can be saved this also has an effect on the production costs of polysilicon the quality of polysilicon with respect to metal values and environmental elements may be improved significantly it has also been found that as a consequence of a standardization of the cleaning plans to the extent that the floors and plant components must be cleaned at least once per week at different locations sic there are scarcely any differences in quality any more between polycrystalline silicon produced at the different locations in the past there were marked quality differences here the causes of which were long unknown since the production and processing operations themselves at the various locations were completely identical surprisingly.