THE MEANING OF
At first glance a germ reduction of 99,99 % seems to be pretty good.
But this is still far away from save...
The expression "LOG X - reduction" describes the effectiveness of a disinfection. It is based on the logarithmus of 10 and shows how many of the virusses, germs, or spores are going to be killed or deactivated.
1 ml of secretion from an infected persons sneezing or coughing contains approximately 1,000,000 viruses.
10 to 100 of them are enough to infect another human. The LOG-factor works as an indicator for microbiological safety.