Log reduction = Risk Reduction
Log reduction is the key measurement of a disinfectant's ability to kill specific organisms. Understanding what those numbers mean can help you separate fact from fiction and has wide reaching implications. People often feel like if their disinfectant/UV light/ Ionizer or other product kills 99.9% of a germ that it’s a really good disinfectant. However, if you start out with a population of one million (which isn’t really that much in the germ world) and you kill 99.9% of the germs, you would still have 1000 organisms left behind on the surface. An infectious dose of some organisms, like SARS-CoV-1, can be as little as 67, meaning there could still be quite a risk if using a 99.9% effective disinfectant.
Basically, the more nines after the period ("."), the more organisms are being killed. According to the EPA, disinfectants need to have a baseline kill of 99.99% (4-logs) of bacteria. At CURIS, our hybrid hydrogen peroxide fog kills 99.9999 (6-logs). So, if you have a 99.9% (3-logs) kill your disinfectant, is it really a disinfectant or is it just a sanitizer?