For example, medical device manufacturers design their sterilization processes for an extremely low SAL, such as 10−6, which is a 1 in 1,000,000 chance of a non-sterile unit.
This usage (technically the multiplicative inverse) results in positive exponents, as in "The SAL of this process is 106".
SALs can also be used to describe the microbial population that was destroyed by the sterilization process, though this is not the same as the probabilistic definition.
Thus a process that achieves a "6-log reduction" (10−6) will theoretically reduce an initial population of one million organisms to very close to zero.
Because of all these ambiguities, contexts in which it is critical to prevent any confusion—such as in the setting of standards—require that SAL terminology be defined carefully and explicitly.