SAL
Sterility Assurance Level
What a definition is not
A definition is SPEQ’s plain-language decode of how a term is used in practice, cited to the documents that define it. It is a practitioner reference, not legal or regulatory advice, it does not replace the definition in the source, and where a regulator’s wording differs the regulator’s wording governs.
The Sterility Assurance Level is the probability that a single unit remains non-sterile after a sterilization process, expressed as a negative exponent — a SAL of 10⁻⁶ means no more than one in a million units is expected to be non-sterile. It is the quantitative target that defines "sterile" for terminally sterilized product.
Because sterility cannot be tested into product (a finite sample can never prove every unit is sterile), sterility is assured by validating a process capable of achieving the target SAL from a known, controlled bioburden. The standard target for terminally sterilized products is 10⁻⁶.
SAL is a property of terminal sterilization, where a defined lethal process acts on the sealed product. Aseptically processed products cannot claim a SAL in the same way, because there is no terminal lethal step; their assurance comes from process design, environmental control, and media-fill validation.
- —Probability of a single non-sterile unit after sterilization.
- —Standard terminal-sterilization target is 10⁻⁶.
- —Sterility is assured by validated process, not by end testing.
- —A true SAL applies to terminal sterilization, not aseptic processing.
ISO 17665 (moist heat) and ISO 11137 (radiation) sterilization standards, SAL 10⁻⁶ convention; EU GMP Annex 1 (2022).
Frequently asked questions
What does SAL stand for?
SAL stands for Sterility Assurance Level.
What is SAL?
The Sterility Assurance Level is the probability that a single unit remains non-sterile after a sterilization process, expressed as a negative exponent — a SAL of 10⁻⁶ means no more than one in a million units is expected to be non-sterile. It is the quantitative target that defines "sterile" for terminally sterilized product.
Which regulations cover SAL?
ISO 17665 (moist heat) and ISO 11137 (radiation) sterilization standards, SAL 10⁻⁶ convention; EU GMP Annex 1 (2022).