The shortwave UVC rays are absorbed in certain areas of the hereditary substance in the cell nucleus (DNA) and as a consequence photo-chemical changes occur.

Explained as a picture two neighbouring information carriers (bases) stick together and with this then become unusable for the copying process itself, which follows the matrix principle. If the number of destroyed information carriers to a particular mass is high enough then the cell will die without having duplicated itself.

As a consequence of this functional procedure UVC rays do not directly kill germs. Correctly spoken they inactivate them and thus prevent them from propagating towards critical masses.