Laboratory & Inspection Practice
Traceability to SI units: what evidence is enough
How to show an unbroken chain of calibrations and references in practice.
Why this matters
Credible accreditation depends on consistent methods, clear decisions, and evidence that stands up to independent review. This publication translates essential expectations into practical steps so teams can prepare, communicate, and operate with confidence.
Key requirements and expectations
- Link technical competence to methods, equipment, and personnel.
- Demonstrate control of critical technical activities.
- Show traceability, uncertainty, and data integrity.
- Maintain records that prove repeatability and validity.
- Traceability must be documented for critical measurements.
- Reference standards require appropriate calibration intervals.
- Records must show uncertainty values at each link.
Evidence and records to prepare
- Method validation or verification records and approvals.
- Calibration certificates and equipment maintenance logs.
- Training and authorization records for technical staff.
- Proficiency testing results and follow-up actions.
- Calibration certificates with uncertainty values.
Common pitfalls to avoid
- Using unvalidated methods or undocumented deviations.
- Incomplete measurement uncertainty or traceability chains.
- Missing training records for authorized signatories.
- Sampling or chain-of-custody steps not controlled.
- Missing traceability documentation for key equipment.
Practical checklist
- Confirm methods are validated or verified for intended use.
- Maintain up-to-date equipment and calibration schedules.
- Document staff competence and authorization limits.
- Review PT and QA results before external assessment.
- Verify traceability for each critical measurement step.