Sterility assurance level (SAL)

The probability that a single unit is non-sterile after sterilisation, usually 10⁻⁶, one in a million, for terminally sterilised products. SAL cannot be measured by testing finished product; it is calculated from the bioburden, its resistance and the validated lethality of the process. Aseptically processed products cannot claim a numerical SAL in the same way, and rely instead on process validation, media fills and environmental control.