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 ISO17011 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 and does provide Z540 accreditation recognition.
ANAB – American National Accreditation Body
ANAB is a non-governmental organization and a wholly-owned subsidiary of American National Standards Institute, Inc. (ANSI), which is a non-profit organization. ANAB provides Z540 accreditation recognition and valuable technical guidance documents, though there is curiosity about the use of European guidance (Euromet document) rather than American standard(s) for calibration practices of scales and balances (TR 2501). Ideally it should be an ASTM, (HB44) American standard or OIML R 111-1, International standard, in my opinion.
PJLA – Perry Johnson Laboratory Accreditation
PJLA operates as a private third-party accreditation body in the United States, affiliated with Perry Johnson Laboratory Accreditation NP, Inc., a Michigan nonprofit established in 2016. PJLA adheres to ILAC, APAC, national, and regulatory requirements to ensure quality service. However, it is notable that PJLA employees themselves conduct assessments, raising questions about their ability to remain fully impartial.
PJLA encourages its CABs to remove Z540.1 or Z540.3 from their scopes, as reflected in Quality Update #92 (December 30th, 2025). This approach is inadvisable, as it limits opportunities to pursue contracts. Contrary to PJLA’s position, Z540 remains the gold standard for sectors such as defense and nuclear power. Historically, Z540 has been paired with a quality standard, with ISO Guide 25 combining ANSI-Z540 and ISO9000 prior to the adoption of ISO17025:2005. Although sometimes referred to as obsolete, Z540 retains its relevance. Calibration laboratories accredited solely to ISO17025, in my opinion, are considered a “light” version compared to those also adhering to Z540. My metrology experience began in 1982 with MIL-STD-45662A—Z540’s predecessor—during my tenure as PMEL-trained personnel in the United States Air Force at Edwards Air Force Base, California. Cleanliness in laboratories was rigorously enforced, a standard subsequently relaxed under ISO 17025. Laboratories that continue to uphold Z540 are distinguished by their high standards and consistently maintain clean environments.
The Future of Z540 Standards
The future trajectory of Z540 standards remains uncertain. While discussions regarding the development of Z540.4 have occurred, details remain unclear. At the recent NCLSI-Cleveland event in July, no changes were enacted. PJLA did not participate in the committee meeting, which may explain their reluctance to promote Z540 accreditation to their CABs—a decision that may ultimately restrict opportunities for those CABs.
Comparing Accreditation Bodies
Significant differences exist among accreditation bodies, directly impacting selection decisions. Price should not be considered as the main determining factor. The relationship between a CAB and its accrediting body is crucial, as it reflects both standards and credibility. IAS, ANAB, and A2LA all address Z540 standards, with A2LA’s requirements generally regarded as more comprehensive. Please note that I serve on both the Measurement Advisory Committee (MAC) and the Accreditation Council (AC) of A2LA, which may influence my perspective on the matter.
Conclusion and Outlook
Although ISO/IEC 17025 serves as the international benchmark, Z540.3 continues to represent the gold standard within specialized U.S. sectors such as defense and nuclear power. Only a limited number of calibration laboratories hold Z540.3 accreditation (e.g., 63 via A2LA, 55 via ANAB). For CABs conforming to Z540 standards, meeting the gold standard affords a competitive advantage
Felipe Narcio, DynaCal/Owner