Calibration Audit Questions and Audit Sequence That We Need to Know

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Audit Schedule

As a calibration tech or Engineer, our responsibility does not end when we performed instrument calibration. One of our responsibilities is also to respond to or support an audit. 

One of the most audited processes of manufacturing industry is the calibration program. The reason is that it is one of the requirements under ISO Standards like ISO 9001 under clause 7.1.5 and of course, ISO 17025:2017 under clause 6.4.

Calibration audit is one of the challenging parts (if not interesting) in internal calibration management if your company is a big one. Almost all areas in the manufacturing floor, calibration audit are expected. Like for example during equipment maintenance, or just even an operator interview. 

Do you do feel uncomfortable every time there is a scheduled audit because you are not sure about your preparations for your calibration program?

Do you always prepare for an incoming audit only to find out that you have non-conformances?

Auditors are not the same, some send their checklist first in advance and some only tell their schedule without the audit checklist.

But regardless of they send an audit checklist or not, we should know what to expect from the auditors.

In this post, I will share with you the most asked questions during a calibration audit that I repeatedly encountered. I will also share the audit sequence that I observed that can help us identify or expect the next audit move or questions.

By identifying all these things and prioritizing its completion, it will help us maintain and prepare more ourselves and our internal calibration lab to pass every audit. (Not a 100% assurance but it is an advantage to know in advance)

In any case that an audit comes, you are already prepared. You can use below questions as an internal audit checklist to perform a self-audit if you are implementing either ISO 9001:2015 calibration audit requirements or ISO 17025 audit requirements.

The Calibration Audit Questions

In the past company that I worked as a Calibration Engineer managing an in-house calibration lab, I always make sure that all documentation that is always checked during audits are regularly updated. 


Because almost every month, an audit is expected, either from internal audit, a 3rd party auditor certifications (ISO 9001 calibration audit) or a customer audit.

As a calibration engineer, our calibration program is in the best shape if we satisfy the queries of our customers, the user of instruments, and the quality personnel, who require us to support them during audits related to calibration.

As much as possible, we do not want any audit findings because sometimes, even this is an opportunity for improvement to us, it looks like we are incompetent if we have an audit finding.

This is one of the reasons why almost half of our time is dedicated to updating and completing documentation.

Below are some of the actual audit questions that I gathered, most of it was taken from a vendor audit checklist usually related to ISO 9001 calibration audit checklist. This is not a complete list of questions but I believe it touches most of the critical points. 

1. Are there documented procedures for control of inspection, measuring, test equipment? Including:

(a) Equipment master list

(b) Calibration schedule

(c) Calibration interval 

(d) Recall list

(e) Calibration record/report

(f) Calibration methods

2. Is the calibration conducted under the specified environmental conditions?

3. Is the personnel in charge of calibration been trained and formally certified?

4. Is equipment verified or re-calibrated at appropriate intervals?

5. Are measuring equipment safeguarded from unauthorized adjustment or re-adjustment?

6. Is there an official approval control system for all equipment to determine accuracy and precision?

7. Are measuring and test equipment re-calibrated when found not meeting the requirement?

8. Are instruments that do not need calibration clearly labeled as such? (Check related post in this link)

9. Are the reference standards or reference materials used for calibrations correctly stored, managed and traceable to International standards (i.e.  NIST)? – Managing a reference standard includes transport, preventive maintenance, and receiving.

10. Is the master standard for internal calibration has the adequate capability (i.e. 10x higher resolution)

11. Is there an appropriate method for storing measuring equipment, tools, and jigs?

12. If a product has been used or tested with equipment found to be out of calibration, is there a process for proper disposition?

13. In case there is a “failed” result in the calibrated equipment, does the procedure define the disposition?

14.  Is there a review process before accepting the services of a 3rd party calibration lab?

15. Are the internal calibration procedures used periodically reviewed and updated?

16. Can you show the measurement traceability (the unbroken chain of comparison) of your reference standards?

17. Is the access to the calibration laboratory effectively controlled?

18. Do you perform intermediate check for your reference standards?

The Calibration Audit Sequence

Actual customer audit
Actual customer audit


Customer audits are the most frequent audits that we encounter in the past company I worked, a manufacturer of ICs (Integrated Circuit) for various usage,  so every now and then a customer audit is expected.

One observation during the audit is that there is a specific audit sequence. These sequences happen most of the audit that I encountered and it is a very helpful guide to trace down the things that are expected to be asked, and in return, we can prepare for it.


Here are the sequences:

First, they will check your master list if you have proper monitoring then they will sample an instrument from that list. If they are in the production line, they will select a certain instrument.

Second, they will inspect the actual sampled instrument.

They will verify for calibration label or ID if:

  • it has one stick on it
  • it is still within the calibration date.
  • It has the same details as indicated in the master list

Third, they will ask for its calibration report.

  • They see to it that there is no out of tolerance reported or displayed in the report.
  • They will check the traceability information 
  • Match the details about the sample like the identification tag or serial number reflected in the label.
  • Other important details including who performs the review once received from the 3rd party lab (this is where we must  be knowledgeable on how to understand and interpret a calibration certificatecheck it out here)

Lastly, they will check who performed the  calibration of the instruments, 

  • if internal, they will ask for the training records, the procedure used, and the calibration certificate of the reference standard used for calibration (in which should be also calibrated by a 3rd party lab under ISO 17025 to ensure traceability)
  • if it is external or  3rd party calibration, they will ask for the accreditation certificate with the scope of accreditation of the Lab (should be accredited to ISO 17025).

These audit sequences are what I mostly observe, the sequence may not exactly in those orders but the majority follow it because of the continues thought process that it can provide to the auditors.

By determining these sequence, it presented on what to improve in my calibration program by focusing on every related detail on the sequence as applicable to every measuring instruments that are being used.


I have presented here the audit questions that I encountered during my time as a Calibration Engineer for an In-house calibration lab following the calibration requirements of ISO 9001 and TS 16949 Standards.
It may be a different industry but I believe the calibration program is almost the same to all. I also share the sequences that I observe that could help us understand more what to expect and prepare during a calibration audit.

These are the things to be expected to be asked during the audit but it is not a complete guide to ensure a properly managed calibration lab. Calibration laboratory management has a dedicated international standard to be used for in-depth knowledge of its management, the ISO 17025. If you want to be accredited as a calibration lab then this is the standard to be used.

Do you have other observation and question guides in mind? Please comment below.

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