The gas scrubber must be designed to ensure that the residence time of gases in the scrubber amounts to approximately 1 second. This may be slightly more or slightly less, depending on the solubility of the components. The scrubber must have a special open packing and special spray nozzles to prevent blockage by biosludge. A bioscrubber consists of a gas scrubber and a biological reactor. In the gas scrubber, to-be-removed components are absorbed from the gas stream by the wash water.  The pollutants that have been absorbed by the wash water are biologically degraded. The purified scrubbing liquid is circulated to the scrubber, where it is able to reabsorb pollutants.