Accreditation Bodies in the United States
The United States currently has six accredited bodies. Each has undergone peer review and auditing, and all are accredited to ISO17012 standards. Unlike most countries, which typically have only one accredited body per economy, the USA is unique in having multiple AB’s—potentially up to 51, including Puerto Rico. Despite mutual recognition among these AB’s, they do not all share the same level of credibility or equivalence.
Review of Major Accreditation Bodies
NVLAP and A2LA
The National Accreditation Volunteer Lab Program (NAVLP), was initially formed to serve the government sector, while A2LA focused on the commerce sector. Over time, these distinctions have blurred, with major companies seeking both accreditations for marketing advantages. NVLAP is generally seen as more prestigious and has a more costly and lengthy accreditation process. Notably, NVLAP offers Z540.1 and does not provide Z540.3 recognition.
IAS – International Accreditation Services
IAS is recognized as the oldest and most prominent accreditation body globally, with over 50 years of service. Led by assessors with world-class credentials, IAS upholds the utmost integrity in its operations. Its primary focus is on testing and inspection, calibration laboratory are NMI, national laboratory level. Recently, I have been fortune to signed a contract as an independent lead assessor to support their endeavor, reflecting the high regard for IAS.
PJLA – Perry Johnson Laboratory Accreditation
Personal experience with PJLA has revealed both positive and negative aspects. The assessments provided valuable insights and facilitated global travel and professional connections. A notable aspect was the rigorous approach to auditing labs transferring to PJLA, adding a unique dimension to the assessments.
In recent years, remote audits have become more common, enabled by technologies like Starlink, allowing for assessments in very remote locations. Despite the enjoyment of performing assessments for PJLA, there were multiple reasons for my disappointment and several concerns with PJLA remain:
PJLA requires labs to include the flex code designation in their scope, which is not mandated by ILAC-G18:01/2024 does not mandate this additional work.
“It is not mandatory for AB’s to offer flexible scopes of accreditation and the guidance provided within this document only applies where the AB chooses to allow this service to CAB.”
Also, PJLA mandates calibration labs (CABs) to provide procedure numbers, methods, and equipment, though ILAC G18 only requires not both equipment and procedure/method. In addition, PJLA has the CAB’s place their internal calibration procedure number(s) which offer no tangible benefit to end users. Unless the procedure is published document, it has no value and diminishes the standing of labs using published methods.
“APPENDIX A
Scope of Accreditation for ISO/IEC 17025 – Calibration Laboratories
ISO/IEC 17011 Sub-clause 7.8.3 Item c) requires the identification of the calibration or measurement method or procedure.”
PJLA encourages CABs to remove Z540.1 or Z540.3 from their scope, as reflected in Quality Update #92 (December 30th, 2025). This is not advisable, as it will reduce opportunities to be able to quote on contracts. Furthermore, contrary to PJLA’s claims, Z540.3 remains the critical Gold Standard, for sectors like defense and nuclear power. Historically, Z540 has always been combined with a quality standard. Before ISO17025, ISO Guide 25 combined Z540 and ISO9000, laid the foundation for ISO17025:2005. Despite being considered obsolete or inactive, Z540 remains relevant. Calibration labs accredited only to ISO17025 are considered a “Light” version compared to those that adhere to Z540.3. You are hearing this from someone who started in metrology with learning MIL-STD-45662A, the grandfather of Z540, Calibration Systems Requirements, PMEL training in the United States Air Force and stationed at Edwards Air Force Base, California. Where there was a saying, “if your laboratory ain’t clean! How can you calibrate anything!?! Ironically, ISO 17025 took that clause out, “good housekeeping”, and probably is an indication as to why labs aren’t up to par. Those labs that are Z540 have that mind set, and go far above the general requirements and most definitely have have a clean laboratory.
As industry evolve under GACA, we must ensure that assessor compensation models remain competive to attract the best technical talent.
The Future of Z540 Standards
The direction of Z540 remains uncertain. Discussions of a possible Z540.4 have surfaced, but its status and potential impact is unclear. At the recent NCLSI-Cleveland event in July, no changes were made regarding Z540. PJLA was unable to join the committee due to being absence at the meeting, which may explain why their stance on not promoting Z540 to their CABs. This decision could be costly for CABs, reducing opportunities to quote on contracts requiring this distinction.
Comparing Accreditation Bodies
The differences and variances between AB's are significant and impact the choice of accreditation body for companies. The relationship between a CAB and its AB is critical, as it reflects the standards and credibility of the organization. IAS, ANAB and A2LA address Z540.3 and Z540.1, with A2LA’s requirements considered a little more robust, in my opinion. ANAB provides valuable technical guidance documents, though there is curiosity about the use of European guidance documents rather than American standard(s) for calibration practices of scales and balances (TR 2501). HB44, NIST 105-1 and NISTIR6969 are the american standards.
Conclusion and Outlook
While ISO/IEC 17025 is the international benchmark, Z540.3 remains the critical Gold Standard for traceability in specialized U.S. sectors like defense and nuclear power. Only a small fraction of calibration labs (e.g., 63 for A2LA, 55 for ANAB) hold Z540.3 recognition.
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