Abstract: The invention relates to biocide-containing active plastics internal elements for the cleaning of gas or air in humidifiers of process gases, gas scrubbers or exhaust air scrubbers in which a gas phase and a liquid phase are in contact with one another, the biocide being selected from the group consisting of 2,3,5,6-tetrachloro-4-(methylsulfonyl)-pyridine, 2,4,4′-trichloro-2′-hydroxy-diphenyl ether, 4,4′-dichloro-2-hydroxyphenyl ether, 2,2′-methylenebis(4-chlorophenol), 4-(2-tert-butyl-5-methylphenoxy)-phenol, 3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea and 2,4,6-trichlorophenol. The invention relates also to the use of the above biocides in plastics internal element for the cleaning of gas or air in humidifiers of process gases, gas scrubbers or exhaust air scrubbers.