A calibration lab is only considered accredited after it has been evaluated by a third-party organization and deemed competent and compliant with the ISO/IEC 17025 standards. These standards, similar to those of ISO 9001, consist of quality management system requirements, but with a deeper technical focus. ISO 17025 accreditation requires the lab to have adequate equipment to perform tests and calibrations. The lab must also have personnel who excel in technical competence and that are proficient in performing tests and calibrations. Assessment for accreditation is broken down into three focal areas, personnel, environment and traceability. If these three areas meet the required standards, the laboratory is then recognized as having the highest level of technical competency and is granted accreditation. Accreditation is then maintained through proficiency testing, which is performed on a regular basis to ensure technical competence.


As stated above, the three key factors that make-or-break accreditation for a lab are the people they have working in it, the environment in which they work in and the traceability of the laboratory equipment. Each focal area has a set of requirements it must meet to be considered ISO 17025 standard, therefore all three are accessed in detail:


Laboratory workers are assessed on technical competence of the equipment and equipment usage. Accreditation requires personnel to understand how to operate all the equipment they use and how it affects the calibration results. In addition, workers need to be capable of calibrating equipment and fully understanding the results. Although these requirements seem pretty basic, they are essential. A laboratory will only be approved to perform accredited calibrations if the personnel understand the measurements they are taking, why they need to take them and how to properly evaluate the results of the measurements to determine the correct operation of the instrument.

Accrediting bodies determine if the lab personnel meet all the requirements listed by supervising and conducting internal and external audits. With interviews and close observation, the accrediting bodies can verify if the laboratory workers are competent and complaint with ISO 17025 standard.


Laboratory environment is assessed by its conditions; temperature control, humidity and barometric pressure are all conditions that are taken into account when assessing for accreditation. It is vital that these conditions, along with sound and vibration levels, are constantly monitored to ensure they do no invalidate results of calibrations or the quality of any measurements. Laboratories are also required to pay close attention to biological sterility, dust, electromagnetic disturbances and radiation. Regulatory housekeeping of the lab is also crucial.

Accrediting bodies will decipher from previous records if the laboratory has complied with the listed requirements. If all ducks are in a row, the laboratory environment will be recognized as meeting the ISO 17025 standard.


The final step in the accreditation process is analyzing equipment traceability. All equipment used to calibrate instruments and conduct measurements must be traceable through an unbroken chain of calibrations or comparisons linking to relevant standards of International System of Units (SI). Calibrations certificates issued through the lab should contain all measurement results, including measurement uncertainty.

Accrediting bodies will often rely on the National Institute of Standards and Technology (NIST) traceable number for each calibration certificate as evidence of traceability. If the laboratory is in compliance of the traceability requirement, it is then deemed up to ISO 17025 standard.

So what’s the big deal with an accredited calibration lab and why should you use one?
Find out here.