Schemes, Proficiency Testing, Traceability & Uncertainty

Technical accreditation schemes

Individual scheme portals — including PTP (proficiency testing providers), RMP (reference material producers), EMAS verifiers and greenhouse gas validation/verification — are published in the Accreditation Schemes directory, each with the applicable regulation, scheme-specific requirements and the scope template.

Proficiency testing (PT) requirements

• Participation in proficiency testing / inter-laboratory comparisons is mandatory wherever a suitable scheme exists for the scope claimed.
• The CAB maintains a PT plan; minimum participation frequency and satisfactory performance criteria are defined per scheme in the normative documents of the respective sector.
• Unsatisfactory PT performance triggers corrective action and may trigger restriction or suspension of the affected scope.

Metrological traceability policy

• Measurements shall be traceable to the SI through an unbroken chain of calibrations, each contributing to the measurement uncertainty, using competent calibration providers (nationally accredited where available).
• Reference materials shall be certified where possible; in-house reference materials require documented homogeneity/stability studies.

Measurement uncertainty rules

• Measurement uncertainty shall be evaluated and reported in accordance with the GUM (JCGM 100) and the relevant scheme guidance; uncertainty budgets shall cover all significant components.
• Calibration laboratories shall publish their CMC values (lowest authorised uncertainty) in the scope of accreditation — see the public registry records.