CIRI Staff

"Log reduction" is a mathematical term (as is "log increase") used to show the relative number of live microbes eliminated from a surface by disinfecting or cleaning.

For example, a "5-log reduction" means lowering the number of microorganisms by 100,000-fold, that is, if a surface has 100,000 pathogenic microbes on it, a 5-log reduction would reduce the number of microorganisms to one.

**Log Reductions**

- 1 log reduction means the number of germs is 10 times smaller
- 2 log reduction means the number of germs is 100 times smaller
- 3 log reduction means the number of germs is 1000 times smaller
- 4 log reduction means the number of germs is 10,000 times smaller
- 5 log reduction means the number of germs is 100,000 times smaller
- 6 log reduction means the number of germs is 1,000,000 times smaller
- 7 log reduction means the number of germs is 10,000,000 times smaller

What is Log Reduction?: Created on June 22nd, 2008. Last Modified on June 22nd, 2008

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