PD CEN TR 16797 — Construction Products Assessment of Release of Dangerous Substances Statistical Assessment of Declared Values (Principles and Technical-Statistical Background)

🏗️ PD CEN TR 16797 is a series of technical reports (TR) published by the British Standards Institution (BSI), concerned with the assessment of release of dangerous substances from construction products — guidance on the statistical assessment of declared values. Prepared by CEN/TC 351 (Construction products: Assessment of release of dangerous substances) with UK participation through BSI committee B/557, the series provides statistical methods for the declaration and verification of release performance of dangerous substances under the EU Construction Products Regulation (CPR) framework. This batch covers Part 1, Principles and rules of application (2015), and Part 2, Technical and statistical background (2015).

💡 The EU CPR requires construction products to declare release performance of dangerous substances and to maintain its stability. The statistical assessment of declared values determines “whether the declared value is reliable and whether product performance is consistently met” — a key link between type testing and factory production control.

1. Scope and Series Composition 📌

This series addresses the assessment of declared values for release of dangerous substances from construction products, supporting in particular:

Setting declared values: how to derive a reliable declared value statistically from test data.
Verification of performance stability: consistency of the declared value with subsequent production testing (AVCP system).
Statistical treatment of test data: sample size, confidence level, and determination rules.

Standard	Edition	Subject	Primary Role
PD CEN/TR 16797-1:2015	2015-08	Principles and rules of application	Defines operational principles of statistical assessment
PD CEN/TR 16797-2:2015	2015-08	Technical and statistical background	Provides methodological basis and statistical background

⚠️ A Technical Report (TR) is a guidance document; it does not replace product technical specifications (hEN) or regulatory requirements. Declaration and verification must still follow the applicable EU regulation, harmonised standards, and certification schemes.

2. Part 1: Principles and Rules of Application 🔬

Part 1 specifies the principles and rules for the statistical assessment of declared values for release of dangerous substances:

Explains the concept of the declared value and the assessment objective.
Gives principles for sampling, grouping, and statistical treatment of test data.
Specifies rules for calculating declared values and conformity determination.
Explains the link with initial type testing (ITT) and factory production control (FPC).

✅ Clear application rules allow different laboratories and notified bodies to process data and derive and verify declared values on a consistent basis, supporting mutual recognition in the EU single market.

3. Part 2: Technical and Statistical Background 🔧

Part 2 explains in depth the technical and statistical background of declared-value statistical assessment:

Gives the principles of the probability distributions, confidence intervals, and tolerance intervals used.
Explains the trade-off between sample size and determination risks (α, β).
Explains outlier and data-handling methods.
Provides the mathematical basis and derivation background for the rules in Part 1.

⚠️ Statistical method is the foundation of declared-value reliability: too small a sample or an improperly set confidence level can make the declared value overly conservative or overly aggressive. Set parameters reasonably based on the Part 2 background.

4. Technical Points and Implementation Advice 📊

Dimension	Part 1 Emphasis	Part 2 Emphasis
Positioning	How to use (operational principles)	Why (statistical background)
Content	Sampling, calculation, determination rules	Distributions, confidence/tolerance intervals, sample size
Audience	Manufacturers, laboratories, notified bodies	Statistics and assessment professionals
Output	Executable assessment process	Mathematical basis for parameter setting

💡 Assessment teams are advised to “set the process with Part 1, set the parameters with Part 2”: first establish the operational rules from sampling to determination, then use the statistical background to justify sample size and confidence level.

5. Engineering Practice and Application Advice 🛠️

🔍 Data management: establish a release test database, recording sampling and test conditions systematically.
📐 Declared-value setting: derive the declared value statistically from type-test data per Part 1, rather than by guesswork.
📋 Stability monitoring: compare the declared value with factory production control test results to detect performance drift promptly.
📊 Method audit: review statistical parameter settings using the Part 2 background to ensure rigour.

6. FAQ ❓

Q: What is a declared value?
A: The value a manufacturer declares for a product performance characteristic (e.g., release of dangerous substances), serving as the baseline for conformity determination and verification.

Q: What does Part 1 cover?
A: The principles and rules of application for the statistical assessment of declared values for release of dangerous substances, including sampling, calculation, and determination.

Q: What does Part 2 cover?
A: It provides the technical and statistical background, including distributions, confidence/tolerance intervals, sample size, and outlier handling.

Q: Is this series mandatory?
A: No. It is a Technical Report (TR), a guidance document; declaration and verification must still follow the regulation and harmonised standards.

Q: How is a declared value made reliable?
A: By deriving it statistically from properly sampled test data and continuously verifying its stability through factory production control.

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