Understanding ISO/IEC 17025 for Test Customers

ISO/IEC 17025 is the international standard for the competence of testing and calibration laboratories. Its current edition was published in 2017 and requires a laboratory to demonstrate that it operates impartially, is technically competent and is able to generate valid results. The standard is not only a management system: it also covers technical requirements such as personnel competence, equipment, metrological traceability, method validation and measurement uncertainty.

ISO 9001 defines an organisation's quality management system; it does not assess the technical correctness of the product or service itself. ISO/IEC 17025 addresses technical competence directly: it demonstrates that a result obtained with a specific method, specific equipment and specific personnel is correct and traceable. A laboratory certified to ISO 9001 therefore does not offer the same assurance about the technical validity of its test results as ISO/IEC 17025 accreditation does.

Accreditation is not a self-declaration. It is granted by the national accreditation body (TÜRKAK in Türkiye) after an on-site assessment and is maintained through regular surveillance assessments. Thanks to international mutual recognition arrangements (ILAC MRA), a report from an accredited laboratory is accepted with the same confidence in other signatory countries.

A laboratory is not accredited "in general"; it is accredited for specific methods. The scope of accreditation lists, item by item, the material or product group tested, the property measured, the standard applied (for example ISO 9227 or ASTM B117) and in most cases the measurement range. This list is publicly available on the accreditation body's website and is the first document to consult when evaluating a quotation.

An accredited laboratory may also perform tests outside its scope, but those results may not carry the accreditation symbol and must be clearly marked as outside the scope on the report. The practical consequence for the customer is simple: the presence of an accreditation logo on a report does not mean that every result in that report is accredited. Whether each individual measurement falls within the scope is indicated separately on the report.

An accredited laboratory is obliged to evaluate the measurement uncertainty of every quantitative result. Uncertainty does not mean the result is "wrong"; it expresses a reasonable level of confidence about the interval within which the true value lies. A coating thickness reported as "52 ± 3 µm (k = 2)" states that, with approximately 95 % confidence, the true value lies between 49 and 55 µm. A result without uncertainty gives you no way to judge how close it really is to a specification limit.

Metrological traceability means that the measurement is linked to SI units through an unbroken chain of calibrations. The balance, the temperature sensor, the thickness gauge and the reference material each hold a documented calibration, and those calibrations were themselves performed by accredited laboratories. Traceability is what makes the results of two different laboratories genuinely comparable.

An important concept introduced with the 2017 edition is the decision rule (clause 7.8.6). If a result is to be declared "conforming" or "non-conforming" against a specification, the way uncertainty is taken into account in that decision must be agreed with the customer in advance and stated in the report. For results close to a limit, this rule can determine whether a product is accepted or rejected, which is why it should be asked about explicitly at the quotation stage.

ISO/IEC 17025 defines the minimum information a report must contain: the identity of the laboratory and the customer, a description of the sample and the date it was received, the method used, the date of testing, the results with their units, measurement uncertainty where applicable, any deviations from the standard method, and the authority of the person approving the results. If the sample was not taken by the laboratory, the report must state that the results apply only to the sample as received.

When reading a report, we suggest looking at the method column, the uncertainty statement and the footnotes before the results table. A note on deviation from the standard method may indicate, for example, a different specimen angle in a salt spray test or a different calibration foil in a coating thickness measurement. Opinions and interpretations, such as the conclusion of a failure analysis, must be clearly separated from the measurement results and marked as such.

NAKTEM develops its quality processes with reference to the requirements of ISO/IEC 17025: calibration and performance checks of equipment, suitable method selection and the necessary verification work, personnel competence, measurement uncertainty where needed, and a clear statement of limitations in reports. NAKTEM is not yet accredited to this standard, so the assurance an accreditation provides, described above, does not apply to NAKTEM reports.

For our customers, the practical meaning is in the report: you can see which method was applied and which instrument and conditions were used. For organisations preparing their own laboratories for accreditation, we also offer ISO/IEC 17025 training and method validation consulting.