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Ensuring NIST Traceability  of your Instrument Calibrations


Few items in this growing global economy are more important to Bill Hirt than ISO/IEC 17025,

an international standard that assesses the technical competency of testing and metrology laboratories providing instrument calibration and NIST-traceable certification services  


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Hirt is the corporate accreditation manager for ACLASS Accreditation Services, an American accreditation body that issues certificates of ISO/IEC 17025 accreditation to laboratories. His worry: that companies needing NIST-traceable testing and calibration of instrumentation fail to understand the nuances of NIST-traceability and what to look for in a metrology lab. Would you please explain what ISO/IEC17025 is and how it pertains to NIST traceability?

Bill Hirt, Ph.D.: The 17025 laboratory standard is sort of a layer of technical competency that laboratories having a quality program must adhere to for international confidence to be built in them. Technical competency?

Bill Hirt, Ph.D.: From sample preparation to analytical testing proficiency to record keeping. The standard covers document control, corrective and preventive actions, environmental conditions, equipment, measurement uncertainty, evidence of traceability, sampling, and so forth. It deals with virtually every aspect of laboratory management and performance. What exactly do you mean by “a layer?”

Bill Hirt, Ph.D.: ISO 9000 is the most common quality standard. It is recognized by more than 120 countries. But for a company, having a quality program in place that adheres to ISO 9000 standards only assures that the company monitors and tracks its work to meet customer needs. 

The 17025 standard layers on top of the ISO 9000 making sure the company uses internationally respected calibration and testing methods—that it maintains properly calibrated reference standards, and that its measurements can track back to what’s called the metrology center in each country. In the U.S., that would be the National Institute of Standards and Technology, or NIST. 

This is a critical layer for metrology labs, because they are calibrating instruments to internationally recognized tolerances accepted by NIST. So, we make sure labs calculate how variable their measurements are—there’s actually an international agreement about how to calculate that variability—and we have labs participate in inter-laboratory comparison tests to make sure results are the same no matter what ISO 17025-accredited lab throughout the world does the testing or calibration. How does an accreditation body like ACLASS carry out the accreditation process?

Bill Hirt, Ph.D.: It is an ongoing process. We return to the laboratory every year to verify their methods, their reference standards, their technicians, and their records to make sure the lab is using good methods and keeping equipment up to date and participating in inter-lab testing. We provide feedback to ensure they can improve and update their methods if necessary. Why is the inter-lab test so important?

Bill Hirt, Ph.D.: We go to laboratories where, for example, a technician will say “I was trained in the Navy. I’ve done this for 20 years. I know I get good results.” Well, if you don’t participate in a round-robin test with other independent laboratories and get similar results, the international community doesn’t have confidence in your tests. So, in order for a company to request accreditation to ISO 17025 they contact you and set up a plan or a program? 

Bill Hirt, Ph.D.:: Basically, yes. As an accreditation body, we hire auditors with competency in specific areas. In the ISO 9000 world the same auditor may cover multiple areas or disciplines. But ISO 17025 auditors are highly specialized; they have a narrow range of focus—for example, electronic equipment or hardness testers or microbiologic testing—so we may need to send two or three different auditors to the same lab. What specifically do the auditors look for?

Bill Hirt, Ph.D.: In the ISO 17025 standard, there are 230 what we call “shall” statements—“You shall do this,” “You shall monitor that”—a lab must comply with. So there are 230 things we need to monitor. We fill out a checklist and verify by interviewing technicians and watching them go through their methods. For a company that needs calibration service, what is the importance of going to an ISO 17025-accredited lab?

Bill Hirt, Ph.D.: It is very critical for international confidence; especially with international trade. Instruments not only come with a manufacturer’s assurance they are functioning and they are accurate, but if they come with a calibration certificate, that certificate may need to be reviewed and the instrument recalibrated once a year—in some cases once a month. Sometimes the manufacturer is the only one who can recalibrate because it’s a unique instrument. Other times not. In either case the instrument owner needs to verify that whoever does the recalibration is able to show their measurements are traceable back to their particular national metrology institute. In the metrology world that traceability is verified if the lab is 17025-accredited. But not all factories are accredited?

Bill Hirt, Ph.D.: That is correct. In a recent interview you seemed to suggest there is some confusion in this area.

Bill Hirt, Ph.D.: We are concerned that some companies seeking accreditation, or which may already be accredited and are trying to add some new test to their list, are assuming if they are having their equipment calibrated by the manufacturer it’s automatically traceable—that no one can calibrate it better than the manufacturer. But that’s not automatic; that’s not guaranteed. That alone does not give the international community confidence. Instruments need to be calibrated by devices that are traceable back to NIST, or most easily demonstrated, by metrology laboratories with ISO 17025 accreditation. So we would like to see more OEMs become accredited in order to provide the data and needed confidence in more and more of our calibration services around the world. How does someone find out if their lab or manufacturer is accredited?

Bill Hirt, Ph.D.: Speak with someone at the lab. Request documentation. Any entity that has received accreditation should be able to provide you with what is called their Scope of Accreditation which states what they have been accredited for. 

Or look for the accreditation icon on the documentation they provided with the instrument. So, if in the U.S. you find the Accreditation Body symbol on your calibration certificate, it denotes it was an accredited calibration and the lab meets all requirements of ISO 17025. That was extremely informative. Thank you for your time.

Footnote : ISO and IEC are acronyms for the International Standards Organization and the International Electrotechnical Commission.


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