ISO 17025 calibration: what it means and when it is required

1. What is ISO 17025?

In addition, iSO/IEC 17025 is the international standard that establishes the competence requirements for calibration and testing laboratories. In short, it is the gold standard for laboratory calibration. A laboratory that is accredited under ISO 17025 has demonstrated that it possesses the technical competence, the correct equipment and reliable procedures to deliver accurate and reproducible measurement results.

Accreditation versus certification

It is important to distinguish between accreditation and certification. Additionally, accreditation under ISO 17025 is granted by a national accreditation body — in the Netherlands this is the Dutch Accreditation Council (RvA). Furthermore, certification, by contrast, is a broader concept with less stringent requirements. Moreover, only accreditation under ISO 17025 is traceable to national and international measurement standards, which is essential for compliance applications.

Difference from ISO 9001

ISO 9001 is a quality management standard for organisations in general. ISO 17025 is more specific: it focuses exclusively on the technical competence of laboratories. Moreover, for example, ISO 17025 requires that every measurement is traceable and that measurement uncertainty is quantified — requirements that ISO 9001 does not impose.

2. Traceability: the core of ISO 17025

The central concept behind ISO 17025 is metrological traceability. Consequently, this means that every measurement is demonstrably linked to national or international measurement standards via an unbroken chain of comparisons.

How does the traceability chain work?

The chain works as follows: your sensor is calibrated against a reference instrument at the laboratory. Therefore, that reference instrument is in turn calibrated at a national metrology institute (in the Netherlands: VSL). VSL calibrates according to international SI units. Similarly, this makes your sensor value indirectly traceable to the international definition of the kelvin.

Why is traceability essential?

Without traceability, a calibration certificate has little evidential value. After all, a measurement that is not traceable cannot be compared with measurements from other laboratories or in other countries. Moreover, the Healthcare and Youth Inspectorate (IGJ) accepts only traceable calibration certificates as evidence during GDP inspections.

3. When is ISO 17025 calibration mandatory?

ISO 17025 calibration is mandatory or strongly required in multiple sectors and situations. In particular, below we provide an overview per regulatory framework.

GDP (pharmaceutical wholesale)

The EU GDP guidelines stipulate that all measuring instruments used for monitoring of critical conditions must be calibrated with traceable certificates. Specifically, concretely, this means annual calibration is required. In practice, temperature sensors, data loggers and thermometers must be calibrated annually by an ISO 17025-accredited laboratory. Moreover, the certificates must be retained as part of the quality dossier.

GMP (pharmaceutical manufacturing)

Under EU GMP guidelines (EudraLex Volume 4), traceable calibration is required for all measuring instruments that affect product quality. Indeed, temperature sensors in production areas and storage locations may therefore only be used if they have been demonstrably calibrated.

HACCP (food industry)

HACCP legislation (Regulation (EC) 852/2004) requires that measuring equipment at critical control points (CCPs) is regularly verified. Although ISO 17025 is not explicitly mentioned, it is the most widely recognised method of demonstrating that calibration is reliable and traceable. Notably, the Dutch Food Safety Authority (NVWA) accepts ISO 17025 certificates as evidence during inspections.

ISO 13485 (medical devices)

ISO 13485 requires the calibration of all measuring equipment that affects product quality. In practice, calibration must be traceable to national measurement standards — which in practice means ISO 17025-certified calibration.

4. What does an ISO 17025 calibration certificate contain?

A valid ISO 17025 calibration certificate contains specific, mandatory information. If any of these elements are missing, the certificate may not be valid for compliance purposes.

Mandatory content of the certificate

First, the certificate states the name and accreditation number of the laboratory, including the logo of the accreditation body (e.g. RvA logo). In addition, it records the unique identification of the calibrated instrument, the measurement method, the reference instruments used during calibration, the measurement results before and after correction, and the measurement uncertainty. Finally, the certificate contains the calibration date and the signature of the responsible staff member.

Measurement uncertainty: what does it mean?

Measurement uncertainty is the range within which the true value lies with a certain confidence level. If the certificate states that the measurement uncertainty is ±0.2°C at a 95% confidence level, this means that the true value lies within ±0.2°C of the measured value with 95% certainty. As a result, this allows you to take this uncertainty into account when setting alarm thresholds.

5. Difference from non-accredited calibration

Not all calibration is equivalent. However, there are three levels of calibration, each with a different level of evidence for compliance.

Level 1: Manufacturer calibration

This is the basic check carried out by the manufacturer. However, manufacturer calibration is generally not traceable and is not accepted as evidence at GDP or GMP audits.

Level 2: Certified calibration (non-ISO 17025)

Some companies offer calibration with a certificate, but without ISO 17025 accreditation. While this is better than manufacturer calibration, formal accreditation and traceability are absent. As a result, this level is insufficient for pharmaceutical compliance.

Level 3: ISO 17025-accredited calibration

This is the highest level. In fact, the laboratory has been independently audited and accredited. Moreover, all measurements are demonstrably traceable to national measurement standards. Evidently, only this level is accepted at GDP, GMP and ISO 13485 audits.

6. How often must you calibrate?

Calibration frequency depends on the applicable regulations, risk level and instrument stability. Accordingly, below we provide guidelines per situation.

Standard frequency

For most applications, annual calibration is the minimum. GDP and GMP guidelines prescribe at least annual calibration of all critical measuring instruments. In addition, annual calibration is the standard for HACCP applications.

When is more frequent calibration necessary?

In certain situations a higher calibration frequency is required. First, for instruments used in critical, high-risk environments. Second, after an incident where the sensor has been dropped or exposed to extreme conditions. Moreover, for instruments that show high drift at periodic calibration.

With Spotzone’s calibration service you automatically receive a reminder when the calibration date is approaching, so you never have an expired certificate.

7. What if a sensor falls outside specification?

If a sensor falls outside the acceptance criteria at calibration — a so-called Out-of-Specification (OOS) result — a fixed procedure must be followed. Subsequently, ignoring an OOS finding is a serious violation at GDP and GMP inspections.

Steps upon an OOS finding

First, the sensor must be removed from service and not used further until the situation has been resolved. In general, you then conduct an impact assessment: were any products stored during the period when the sensor was outside specification? In addition, all findings and measures must be documented in writing. Finally, you replace or repair the sensor and have it re-calibrated before it is put back into use.

Reviewing the storage period

If the impact assessment reveals that the deviation was significant and products may have been stored outside the required temperature range, a product evaluation must take place. In the worst case, this may lead to a recall. Overall, this is why timely calibration and alarm monitoring are essential.

8. Calibration with Spotzone

Spotzone offers integrated ISO 17025-certified calibration as part of the monitoring subscription. Particularly, this means you do not need to find a separate supplier. As a result, calibration is not an additional administrative burden, but an automated part of your compliance process.

Advantages of calibration via Spotzone

• ISO 17025-certified calibration certificates — automatically stored in the platform
• Traceable to VSL (national metrology institute of the Netherlands)
• Automatic reminders before the calibration expiry date
• Directly exportable certificates for audits
• Calibration history overview per sensor in the dashboard

View our calibration service or schedule a free demo to see how we handle this.

Frequently asked questions about ISO 17025 calibration

Below we answer the most frequently asked questions about ISO 17025 calibration, so you have all the information readily available.

General questions about ISO 17025

Questions about certificates and procedures

Questions about laboratories and frequency