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Reference.org
Log reduction
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<p>Log reduction is a measure of how thoroughly a <a href="/facts/Decontamination_process/WcMsfTdb">decontamination process</a> reduces the <a href="/facts/Concentration/wqBmz5od">concentration</a> of a <a href="/facts/Contaminant/RC0L7KRy">contaminant</a>. It is defined as the <a href="/facts/Common_logarithm/q6EhDnWk">common logarithm</a> of the ratio of the levels of contamination before and after the process, so an increment of 1 corresponds to a reduction in concentration by a factor of 10. In general, an <i>n</i>-log reduction means that the concentration of remaining contaminants is only 10−<i>n</i> times that of the original. So for example, a 0-log reduction is no reduction at all, while a 1-log reduction corresponds to a reduction of 90 percent from the original concentration, and a 2-log reduction corresponds to a reduction of 99 percent from the original concentration. </p>