CEN/TR 14542:2003

Overview

CEN/TR 14542:2003 - Durability of wood and wood-based products - provides guidance on the validity of test results obtained under earlier versions of a test standard when that standard is revised. Prepared by CEN/TC 38, this Technical Report addresses how to treat existing biological test data used to evaluate the efficacy of wood preservatives after a test method has been updated.

Key topics

• Normative annex requirement
  Revised or new test standards should include an annex addressing the validity of results from former versions; the presumption is that prior valid results should remain acceptable unless shown otherwise.
• Scope of applicability
  Focused on biological test methods for assessing wood-preservative efficacy relevant to prescribed use classes.
• Principles for accepting former test results
  • Successful practical use (≥10 years): If a product has been proven in practice for at least ten years without failures due to preservative inefficacy, previous test results are accepted without limitation (applicant must prove successful use).
  • Field-tested products: Results from field tests remain valid even if the related laboratory test standard is revised.
  • Expert assessment for other products: Experts must judge whether procedural changes cause:
    • Minor influence → no re-testing required, or
    • Marked influence → limited or full re-testing required, proportionate to the potential effect on efficacy judgment.
  • Ring-test equivalence: No re-testing is needed when inter-laboratory ring-tests during the development of the revised standard demonstrate equivalence between old and new procedures.
  • Transition period: When replacing a standard with a new procedure, the new standard should specify a transition time.

Applications

• Standards writers - use as drafting guidance to include validity annexes in revisions.
• Testing laboratories and accreditation bodies - apply principles to determine when re-testing is required and accept historical data.
• Manufacturers and product applicants - prepare evidence of long-term practical use or field-test data to support claims of continued validity.
• Regulators and certification schemes - adopt consistent criteria for transitioning to revised test methods and recognizing legacy results.

Related standards

• EN 599-1 (Durability of wood and wood-based products - performance of preventive wood preservatives as determined by biological tests) - CEN/TR 14542 recommends including its general principles as an informative annex to EN 599-1.

Keywords: CEN/TR 14542, durability of wood, wood-preserving chemicals, test result validity, revised standards, biological test methods, ring-tests, field tests, re‑testing.