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BSI PD CEN/TR 16797-2:2015

BSI PD CEN/TR 16797-2:2015

$215.11

Construction products: Assessment of release of dangerous substances. Guidance on the statistical assessment of declared values – Technical and statistical background

Published By Publication Date Number of Pages
BSI 2015 124
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This Technical Report provides guidance on the statistical assessment of declared values with respect to the release, emission and/or content of dangerous substances. This report provides statisticallybased criteria for type-testing (TT), further-testing (FT) and where a product has been shown to be consistent with measured values for the release, emission or content that are significantly below the declared values, the point where no-further-testing (NFT) is permitted.

A series of fundamental principles are defined in CEN/TR 16797-1 and two statistical approaches are defined. The first approach is to use assessment by variables and this approach requires the data to be normally or log-normally distributed. This approach is recommended as the default option. The alternative approach based on assessment by attributes is appropriate for data sets that are not normally or log-normally distributed. The downside to this form of assessment is that more test data are needed for the same level of reliability. CEN/TR 16797-1 introduces these assessment procedures and CEN/TR 16797-2 provides more detail and the statistical proof that they satisfy the principles defined in CEN/TR 16797-1. With both of these approaches the minimum frequency of testing is a function of the distance between the mean value and declared value and the variability of the data set, i.e. the sample standard deviation.

To reduce the costs of testing, production plants producing a similar product may share data, e.g. be grouping the product into clusters for statistical assessment of declared values. Rules for the use of clusters are given in this document.

This document also contains rules for identifying outliers within a data set and guidance on using tests other than the reference method for FT.

A list of tasks for product technical committees is given in this document as is a model clause for including in product standards and rules of applications that may be cited in the product standard or copied into product standards.

PDF Catalog

PDF Pages PDF Title
4 Contents Page
6 European foreword
7 0 Introduction
0.1 General
0.2 Background
8 0.3 Assessment of construction products
10 Figure 1 — Possibilities of WFT, FT and NFT for construction products
11 0.4 Reading guide to CEN/TR 16797-2
0.4.1 General introduction
0.4.2 Rules of application
0.4.3 Statistical background
0.4.4 Annexes
12 1 Scope
2 Terms, definitions, abbreviations and symbols
2.1 Terms and definitions
16 2.2 Abbreviations and symbols
18 3 Context
19 4 Quality level of performance with respect to the release, emission or content of RDS
5 Methods for statistical assessment of declared values for RDS
5.1 Goal of the assessment
5.2 Assessment of the production
21 5.3 Assessment of clusters
22 5.4 Assessment of no-further-testing
23 Figure 2 — WFT-FT-NFT procedures for construction products option 1: third party control
24 Figure 3 — WFT-FT-NFT procedures for construction products option 2: update dossier
25 5.5 Methods of assessment
5.5.1 Introduction
5.5.2 Assessment by variables
26 5.5.3 Assessment by attributes
5.6 Description of the assessment procedure
5.6.1 Type testing
27 Figure 4 — TT procedure, example of assessment by variables based on 5 test values. In the case of NFT more requirements need to be satisfied, see 5.4
5.6.2 Further-testing
28 Figure 5 — FT procedure based on 5 test values and assessment by variables. In the case of NFT more requirements need to be satisfied, see 5.4. In the case of batch testing a return to random testing is delayed, see 6.2.2
5.6.3 Clusters
31 Figure 6 — FT cluster system based on 10 test values and assessment by variables
5.6.4 No-further-testing
5.7 Banned substances
32 6 Assessment by variables
6.1 Single production units
6.1.1 Type testing
Table 1 — Criteria for ending TT for a single production unit – assessment by variables
33 6.1.2 Further-testing
34 Table 2 — Test frequency for a single production unit – assessment by variables
35 6.1.3 Rule of application for products where the test values are significantly below the declared value (Gamma rule)
Table 3 — Test frequency – gamma factor
6.1.4 Rule of application for products where a small number of test results may be expected
36 Table 4 — Criteria for ending TT – Gamma rule for a coefficient of variation of 0,65
6.2 Cluster of production units
6.2.1 Type testing
Table 5 — Test frequency for random testing – Gamma rule for a coefficient of variation of 0,65
37 Table 6 — Criteria for ending TT for a cluster – assessment by variables
38 6.2.2 Further-testing
Table 7 — Test frequency for a cluster – assessment by variables
39 6.2.3 Rule of application for cluster products where the test values are significantly below the declared value (Gamma rule)
Table 8 — Test frequency – gamma factor
6.3 No-further-testing
Table 9 — Criteria for NFT – assessment by variables
40 6.4 Handling values lower than the detection limit
6.5 Identifying outliers
41 Table 10 — Critical value GP for testing outliers
6.6 Choosing a declared value
42 7 Assessment by attributes
7.1 Single production units
7.1.1 Type testing
Table 11 — Criteria for ending TT for a single production unit – Assessment by attributes
43 7.1.2 Further-testing
Table 12 — Test frequency for a single production unit – Assessment by attributes
44 7.2 Cluster of production units
7.2.1 Type testing
Table 13 — Criteria for ending TT for a cluster – assessment by attributes
45 7.2.2 Further-testing
Table 14 — Test frequency for a cluster – assessment by attributes
46 7.3 No-further-testing
Table 15 —Criteria for NFT – assessment by attributes
7.4 Handling values lower than the detection limit
7.5 Identifying outliers
47 7.6 Choosing a declared value
8 Statistical principles of the rules of application
8.1 Introduction
8.2 Assessment of a production part
48 Figure 7 — Testing consecutive production parts in case of randomly testing every 1 of 2 batches
49 Figure 8 — Criteria for a conforming part of the production – OC-curves for 1, 5 and 20 samples based on assessment by variables
50 Figure 9 — Probability of random testing and batch testing – assessment by variables 5 batches per production part (n = 5, k = 0,69); P{random testing} + P{batch testing} = 1
51 Figure 10 — Change of the histogram (left) and distribution (right) of three different product qualities (from top to bottom a production with 10 %, 30 % and 60 % > LD) due to combining random testing and batch testing – assessment by variables 5 batc…
52 8.3 Test error
53 8.4 Assessment by variables
8.4.1 Type testing and further-testing
Figure 11 — Probability of ending TT – assessment by variables (OC-curves)
54 Figure 12 — Probability of achieving random testing for FT – assessment by variables (OC-curves)
8.4.2 Test frequency for further-testing
55 Table 16 — Critical values for kn for different percentiles and a probability of 90 %
Figure 13 — Probability of achieving frequency criteria – assessment by variables (OC-curves)
56 Figure 14 — Probability of achieving a specific testing frequency for n = 5 – assessment by variables (curves have been derived from the OC-curves of Figure 13)
Figure 15 — Range of possible k5 values for n = 5 — Assessment by variables
57 Figure 16 — Percentage of batches which are actually tested – assessment by variables (n = 5)
58 8.4.3 Gamma rule
8.4.4 No-further-testing
59 Figure 17 — Probability of passing NFT – assessment by variables (OC-curves)
8.5 Assessment by attributes
8.5.1 Type testing and further-testing
60 Figure 18 — Probability of ending TT – assessment by attributes (OC-curves)
Figure 19 — Probability of achieving random testing for FT – assessment by attributes (OC-curves)
61 Table 17 — Values for n and na for different percentiles and a probability of 90 %
Figure 20 — Probability of passing frequency criteria – assessment by attributes (OC-curves)
8.5.2 No-further-testing
62 Figure 21 — Probability of achieving NFT – assessment by attributes
8.6 Consumer’s and producer’s risk
8.6.1 Acceptance and non-acceptance of batches that exceed the declared value
8.6.1.1 General
8.6.1.2 OC-curve
63 Figure 22 — Probability of accepting and rejecting batches – assessment by variables 5 batches per production part (n = 5,k = 0,69); P{accepting a batch > LD} + P{accepting a batch ≤ LD} + P{rejecting a batch > LD} + P{rejecting a batch ≤ LD} = 1
8.6.1.3 Reduced testing
64 Figure 23 — Probability of accepting and rejecting batches with respect to the OC-curve combined with reduced testing – Assessment by variables 5 batches per production part
8.6.1.4 Criterion for returning from batch testing to random testing
65 Figure 24 — Probability of accepting and rejecting batches with respect to the OC-curve, reduced testing and imposed delay – Assessment by variables 5 batches per production part
8.6.2 Estimation of the consumer’s risk
66 Figure 25 — Consumer’s risk – assessment by variables
Figure 26 — Consumer’s risk – assessment by attributes
8.6.3 Practical approach
67 9 Additional sampling requirements
9.1 General
68 9.2 Probabilistic sampling
70 Figure 27 — Number of samples and increments at 90 % confidence (α = 10 %, z1/2α = 1,645)
Table 18 — Number of increments and samples
9.3 Judgemental sampling
10 Indirect tests
10.1 General
71 10.2 Correlation
72 10.3 No correlation
73 Annex A Examples of the rules of application
A.1 EXAMPLE 1: Assessment by variables for a single production unit
76 A.2 EXAMPLE 2: Assessment by attributes for a single production unit
79 A.3 EXAMPLE 3: Assessment by variables for a cluster
82 A.4 EXAMPLE 4: Assessment by attributes for a cluster
86 A.5 EXAMPLE 5: No-further-testing (NFT) – assessment by variables
89 Annex B Distribution of test values
B.1 General
B.2 Leaching
90 Table B.1 — Distribution of leaching data of 16 different construction products
B.3 Release into air
B.4 Content
91 Table B.2 — Distribution of content data of 7 different construction products
92 Annex C Checklist for Technical Committees
94 Annex D Model clauses for product standards
D.1 Introduction
D.2 Model clause for product standards
D.2.1 Statistical assessment of declared values for dangerous substances
Table D.1 — Substances listed in notified regulations for
95 D.2.2 No-further-testing
D.3 Rules of application for single production units
D.3.1 Rule of application using assessment by variables
D.3.1.1 General
96 D.3.1.2 Type testing
97 Table D.2 — Assessment by variables: Conformity criteria for TT
D.3.1.3 Further-testing
98 Table D.3 — Assessment by variables: Minimum test frequency for FT
D.3.1.4 No-further-testing
99 Table D.4 — Assessment by variables: Criteria for NFT
D.3.2 Rule of application using assessment by variables and the gamma rule
D.3.2.1 General
100 D.3.2.2 Type testing
101 Table D.5 — Assessment by variables: Conformity criteria for TT for assessment by the gamma rule for data that have a coefficient of variation of 0,65
D.3.2.3 Further-testing
102 Table D.6 — Assessment by variables: Minimum test frequency for FT for testing by the gamma rule for data that have a coefficient of variation of 0,65
D.3.2.4 No-further-testing
103 D.3.3 Rule of application using assessment by attributes
D.3.3.1 General
D.3.3.2 Type testing
104 Table D.7 — Assessment by attributes: Conformity criteria for TT
D.3.3.3 Further-testing
105 Table D.8 — Assessment by attributes: Minimum frequency of testing for FT
D.3.3.4 No-further-testing
106 Table D.9 — Assessment by attributes: Criteria for NFT
D.4 Rules of application for clusters of production units
D.4.1 General
D.4.2 Management of a cluster of production units
107 D.4.3 Rule of application using cluster assessment by variables
D.4.3.1 Type testing
D.4.3.2 Further-testing
D.4.3.3 No-further-testing
108 Table D.10 — Cluster assessment by variables: Conformity criteria for TT
109 Table D.11 — Cluster assessment by variables: Minimum test frequency for FT
D.4.4 Rule of application using cluster assessment by attributes
D.4.4.1 Type testing
110 Table D.12 — Cluster assessment by attributes: Conformity criteria for TT
111 D.4.4.2 Further-testing
Table D.13 — Assessment by attributes: Minimum frequency of testing for FT
D.4.4.3 No-further-testing
112 D.5 Identifying outliers
Table D.14 — Critical value GP for testing outliers
113 D.6 Use of indirect tests
D.6.1 General
D.6.2 Correlation
114 D.6.3 No correlation
115 Annex E Critical values for assessment by variables
119 Annex F Gamma factor
122 Bibliography

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BSI PD CEN/TR 16797-2:2015
$215.11