What is clean?

What cleanliness means can also be defined in terms of the area from which one wishes to define it. In the fields of electrical engineering and the automotive industry, the focus tends to be on technical cleanliness, whereby one concentrates in advance on protection against contamination by particles or on the absence of certain chemical impurities on the surface.

In healthcare, on the other hand, one can distinguish between the terms ‘making clean’ as the reduction of the number of microorganisms and ‘making sterile’ and ‘making germ-free’ as the active removal of microorganisms [2]. Similarly, one must differentiate between disinfection and cleaning. Swissmedic defines the terms as follows [3]:

• Disinfection: disinfection causes a reduction in the number of pathogens on surfaces or objects so that they can no longer cause infection or pathogen transmission (elimination of pathogenic germs). The microbial reduction here is >4 log levels for fungi and viruses and >5 log levels for bacteria.
• Cleaning: Removal of contamination to the extent necessary for its treatment and subsequent use.