Recooling systems can become sources of airborne pathogens. The owner/operator is obligated to minimise the risk ensuing from such installations. This standard provides guidance for hygienically sound operation of recooling systems. The standard applies to existing and new evaporative cooling installations and apparatus where water is trickled or sprayed or can in any other way come into contact with the atmosphere with the exception of natural-draugth cooling towers with power dissipations of more than 200 MW. Whether the cooling water is itself the cooling medium in the process or takes over the heat via a heat exchanger from a primary cooling circuit is