ILAC Policy on Traceability of

Measurement Results

ILAC-P10:2002

© Copyright ILAC 2002

ILAC encourages the authorised reproduction ofits publications, or parts thereof, by organisationswishing to use such material for areas related toeducation, standardisation, accreditation, goodlaboratory practice or other purposes relevant toILAC’s area of expertise or endeavour.

Organisations seeking permission to reproducematerial from ILAC publications must contact theILAC Chair or Secretariat in writing or viaelectronic means such as email.

The request for permission should clearly detail1) the ILAC publication, or part thereof, for

which permission is sought;2) where the reproduced material will appear

and what it will be used for;3) whether the document containing the ILAC

material will be distributed commercially,where it will be distributed or sold, and whatquantities will be involved;

4) any other background information that mayassist ILAC to grant permission.

ILAC reserves the right to refuse permissionwithout disclosing the reasons for such refusal.

The document in which the reproduced materialappears must contain a statement acknowledgingILAC’s contribution to the document.

ILAC’s permission to reproduce its material onlyextends as far as detailed in the original request.Any variation to the stated use of the ILACmaterial must be notified in advance in writing toILAC for additional permission.

ILAC shall not be held liable for any use of itsmaterial in another document.

Any breach of the above permission to reproduceor any unauthorised use of ILAC material is strictlyprohibited and may result in legal action.

To obtain permission or for further assistance,please contact:The ILAC Secretariat,c/- NATA,7 Leeds Street,Rhodes, NSW, Australia, 2138,Fax: +61 2 9743 5311,Email: ilac@nata.asn.au

Guidelines for the

Preparation, Layout

and Numbering of

ILAC Publications

ILAC Policy on Traceabilityof Measurement Results

ILAC-P10:2002

ILAC-P10:2002

Page 4

ILAC Policy on Traceability of Measurement Results

PREAMBLE

ILAC has the objective to develop and maintain aMutual Recognition Arrangement between thenationally recognised accreditation bodies. Toensure confidence between the accreditationbodies, it is considered necessary to have appropri-ate harmony between key practices and policies ofthe accreditation bodies. Traceability of measure-ment results is a fundamental topic for develop-ment of a harmonised policy.

ILAC identified a number of features of traceabil-ity of measurement results, which would bedesirable in an ideal world (see chapter 2). How-ever, it is recognised that the complete achieve-ment of such an ideal could take many yearsbecause some of the features of an ideal interna-tional system for traceability are outside the directcontrol of ILAC. ILAC will continue to co-operateclosely with the CIPM and BIPM and will continueto encourage the further development,harmonisation and completion of those featuresby external bodies, such as the BIPM, the RegionalMetrology Organisations and the individualnational metrology institutes in the economies ofILAC members.

Among others due to the urgent request of ILACseveral years ago, the CIPM (International Com-mittee for Weights and Measures), being theGoverning Board of the BIPM, has realized underthe scope of the Metre Convention a CIPM MRAon the Mutual Recognition of National Measure-ment Standards and of Calibration and Measure-ment Certificates issued by National MetrologyInstitutes. This CIPM MRA is now being imple-mented.

Factors, which influence the development andimplementation of a harmonised ILAC policy ontraceability of measurement results, include thefollowing:

(a) Few economies have the complete range ofnational measurement standards and bestmeasurement capabilities needed to supportthe calibration and testing needs of allpotential applicants for accreditation in theireconomy;

(b) Access to suitable national measurementstandards is more complex in those econo-mies whose national metrology institutes donot hold the relevant standards nor have thebest measurement capabilities needed to

support the calibration and testing activitiesof all accredited laboratories in theireconomies;

(c) The concept of traceability of measure-ment results in fields such as the chemicaland biological sciences is still partly underinternational debate and progression to-wards a unified understanding and use ofthis concept is not yet complete;

(d) The role of certified reference materials inproviding traceability of measurementresults has not yet been fully establishedinternationally;

(e) There are cases in almost every economywhere some links (i.e. calibration laborato-ries) in the traceability chain are not accred-ited.

PURPOSE

To provide a policy on traceability of measure-ment results which is intended to be implementedby ILAC members and to encourage the develop-ment of supporting bodies such as CIPM/BIPM.

Unless otherwise noted in the text for someclauses, this policy is effective as of 1 January2003.

AUTHORSHIP

This publication was initially prepared by the ILACTechnical Accreditation Issues Committee andendorsed for publication by the ILAC GeneralAssembly in 2001.

ILAC-P10:2002

Page 5

ILAC Policy on Traceability of Measurement ResultsTable of Contents

Preamble ................................................................................................................................................ 4

Purpose ................................................................................................................................................... 4

Authorship .............................................................................................................................................. 4

1 ILAC Concept of Traceability of Measurements Results .................................................. 6

2 ILAC Policy on Traceability of Measurement Results ...................................................... 6

3 Future Developments .......................................................................................................... 7

4 References ................................................................................................................................ 7

ILAC-P10:2002

ILAC-P10:2002

Page 6

ILAC Policy on Traceability of Measurement Results

1 ILAC CONCEPT OFTRACEABILITY OFMEASUREMENTS RESULTS

1.1 The criteria on traceability which laborato-ries have to meet are laid down in chapter5.6 of ISO/IEC 17025 – General requirementsfor the competence of testing and calibrationlaboratories.

1.2 ILAC has published a guidance documenton traceability of measurement results.(ILAC-G2:1994 is Traceability of Measure-ments). This document is in harmony interms of the concept of traceability ofmeasurement results and should be con-sulted for a more detailed understanding ofthe topic.

1.3 The formal definition of traceability isgiven in the International Vocabulary of Basicand General Terms in Metrology (VIM- 1993)as: ”6.10 traceability: property of theresult of a measurement or the value of astandard whereby it can be related to statedreferences, usually national or internationalstandards, through an unbroken chain ofcomparisons all having stated uncertainties.”

1.4 Traceability (as given in both ILAC G2 andVIM) is characterised by:(a) an unbroken chain of comparisons

going back to stated references accept-able to the parties, usually a national orinternational standard;

(b) uncertainty of measurement; theuncertainty of measurement for eachstep in the traceability chain must becalculated or estimated according toagreed methods and must be stated sothat an overall uncertainty for the wholechain may be calculated or estimated;

(c) documentation; each step in the chainmust be performed according to docu-mented and generally acknowledgedprocedures; the results must be re-corded.

(d) competence; the laboratories or bodiesperforming one or more steps in thechain must supply evidence for theirtechnical competence (e.g. by demon-strating that they are accredited);

(e) reference to SI units; the chain ofcomparisons must, where possible, endat primary standards for the realisationof the SI units;

(f) calibration intervals; calibrations mustbe repeated at appropriate intervals; thelength of these intervals will depend ona number of variables (e.g. uncertaintyrequired, frequency of use, way of use,stability of the equipment).

2 ILAC POLICY ON TRACEABILITYOF MEASUREMENT RESULTS

ILAC Member Bodies agree that thefollowing policy on traceability of measure-ment results be adopted by the regionalbodies and by ILAC Member Bodies.

(a) Laboratories accredited by ILAC MemberBodies shall be able to demonstrate thatcalibration of critical equipment, and hencethe measurement results generated by thatequipment, relevant to their scopes ofaccreditation, are traceable to the Interna-tional System of Units (SI units). Wheresuch traceability is not technically possibleor reasonable, the laboratory and the clientand other interested parties may agree tousing certified reference materials providedby a competent supplier or using specifiedmethods and/or consensus standards thatare clearly described and agreed by allparties concerned; (See: Notes 1and 2).

Note 1:It is recognised by ILAC that, due to the natureof some tests, it is not possible, realistic or relevantto expect traceability of measurement results to bedemonstrated. ILAC Member Bodies have agreedto investigate this issue and develop guidelines onsuch exceptions and areas where requirements fortraceability are difficult to apply.Note 2:“Critical “ equipment used by testing and calibra-tion laboratories is considered by ILAC to be thoseitems of equipment necessary to perform a test orcalibration from the scope of accreditation andwhich have a significant effect on the uncertainty ofmeasurement of test or calibration results. ILACMember Bodies have agreed to investigate this issuefurther and to develop guidelines to differentiatebetween calibrations that are critical and lesscritical and to indicate how in the latter case thetraceability requirements may be less rigorous.

(b) Accredited calibration laboratories, forequipment and calibrations relevant to theirscopes of accreditation, shall in all cases,where possible, derive their traceabilityeither:

ILAC-P10:2002

Page 7

ILAC Policy on Traceability of Measurement Results

! directly from an appropriate nationalmetrology institute or

! from a calibration laboratory that candemonstrate competence, measurementcapability and traceability with appropri-ate measurement uncertainty, e.g. anaccredited calibration laboratory (See:Notes 3 and 4).

Note 3:It is recognised by ILAC that in some economiescalibrations performed by verifying authoritiesappointed under their economies’ legal metrologyframeworks are also accepted. Legal metrologylaboratories should also be encouraged by Accredi-tation Bodies and through their international andregional organisations to seek accreditation toensure competence and safeguard proper traceabilityof their measurement and calibration results and tomake their competence transparent to third parties.Note 4:ILAC considers an “appropriate “ nationalmetrology institute to be one that participatesregularly and successfully in relevant internationalinterlaboratory comparisons performed by BIPMand/or by regional metrology bodies.ILAC encourages BIPM and regional bodies toconduct and publish details of as broad a range ofinternational comparisons as possible to providetransparency on the equivalence and linkages ofnational measurement standards, which underpinaccreditation activities. ILAC has taken note thatthe results of international comparisons carriedout in the scope of the Metre Convention arepublished in Appendix B of the CIPM MRA (www.bipm.org).

(c) Where the concept of traceability is relevantand technically possible, accredited testinglaboratories shall be required by ILACMember Bodies to ensure the traceabilityof their in-house calibration and/or accred-ited test results to an external calibrationprovider that is accredited for suitably smalluncertainties or that can otherwise demon-strate its competence, or to a nationalmetrology institute or national referencelaboratory or to a certified referencematerial or mutual consent standard oragreed method (See: Notes 3 and 4).

(d) ILAC shall require applicant accreditationbodies, seeking membership in its MutualRecognition Arrangement or a RegionalMultilateral Arrangement, to provide thefollowing details when submitting theirapplications:

(i) the sources of traceability to nationalstandards of measurement available toaccredited or applicant laboratories intheir economy and details of how thesestandards are linked to internationallyrecognised primary standards;

(ii) the best measurement capabilities avail-able from the sources in (i) above foreach field of measurement provided toaccredited laboratories in their economy;and

(iii) the accreditation body’s written policy onacceptable sources of traceable measure-ment results.

Note 5:ILAC has taken note that the informationnecessary for accreditation bodies to demonstrate thetraceability of their accredited laboratories ispublished in Appendix C of the CIPM MRA (www.bipm.org). This will ensure effective implementa-tion of clauses 3(d)(i) and (ii).

(e) Laboratories holding only managementsystems certification will be deemed to havenot demonstrated the necessary technicalcompetence.

3 FUTURE DEVELOPMENTS

ILAC Member Bodies agree that the abovepolicy will need to be reviewed in light ofexperience in its implementation and asrelated international influences becomefurther developed such as: greater use ofuncertainties in the chemical and biologicalsciences; greater international transparency inthe certification of reference materials; andavailability of additional information fromBIPM, APMP, COOMET, EUROMET,SADCMET and SIM on the equivalenceand/or linkages between the standards ofnational metrology institutes or nationalreference laboratories.

4 REFERENCES

! ILAC G2: 1994 – Traceability of measurements.! International vocabulary of basic and general terms

in metrology – BIPM, IEC, IFCC, ISO,IUPAC, IUPAP, OIML (1993).

! Guide to the Expression of Uncertainty in Mea-surement - BIPM, IEC, IFCC, ISO, IUPAC,IUPAP, OIML (corrected and reprinted,1995).

! ISO/IEC 17025:1999 – General requirementsfor the competence of testing and calibrationlaboratories

! CITAC – CITAC Policy on traceability! CIPM MRA

The International Laboratory Accreditation Cooperation (ILAC) is the principal international forum for the exchange of ideas and information on laboratory accreditation.

Established in the late 1970s, ILAC membership has grown rapidly and includes representatives from the world’s major laboratory accreditation systems in Europe, Asia, North America, Australia and the Pacifi c. Countries that are developing their own laboratory accreditation systems are also welcome to participate and contribute.

ILAC operates a series of committees which investigate issues such as the harmonisation of international laboratory accreditation practices, the effectiveness of mutual recognition agreements in facilitating trade and the promotion of the aims and awareness of laboratory accreditation around the world.

There are regular meetings of individual ILAC committees as well as a major plenary meeting of all ILAC members.

The activities of ILAC affect a diverse range of areas including standardisation, accreditation, certifi cation, testing, calibration, and regulation in both the public and private sectors.

ILAC has a comprehensive website at www.ilac.org which contains a wealth of information regarding accreditation, testing, trade related publications and other information of interest to industry, regulators, government, trade bodies, laboratories,

accreditation bodies, and users of testing and calibration services.

The following ILAC publications are available free of charge on the ILAC website at www.ilac.org:

BrochuresILAC Information BrochureWhy Use An Accredited Laboratory?Why Become An Accredited Laboratory?How Does Using an Accredited Laboratory Benefi t Government & Regulators?The Advantages of Being An Accredited Laboratory (86 kb) Information Documents (I Series)ILAC-I1:1994 Legal Liability in TestingILAC-I2:1994 Testing, Quality Assurance, Certifi cation and AccreditationILAC-I3:1996 The Role of Testing and Laboratory Accreditation in International TradeILAC-I4:1996 Guidance Documents for the Preparation of Laboratory Quality Manuals

Guidance Documents (G Series)ILAC-G2:1994 Traceability of MeasurementILAC-G3:1994 Guidelines for Training Courses for AssessorsILAC-G4:1994 Guidelines on Scopes of AccreditationILAC-G7:1996 Accreditation Requirements and Operating Criteria for Horseracing LaboratoriesILAC-G8:1996 Guidelines on Assessment and Reporting of Compliance with Specifi cationILAC-G9:1996 Guidelines for the Selection and Use of Certifi ed Reference MaterialsILAC-G10:1996 Harmonised Procedures for Surveillance & Reassessment of Accredited LaboratoriesILAC-G11:1998 Guidelines on Assessor Qualifi cation and CompetenceILAC-G12:2000 Guidelines for the Requirements for the Competence of Reference Material ProducersILAC-G13:2000 Guidelines for the Requirements for the Competence of Providers of Profi ciency Testing SchemesILAC-G14:2000 Guidelines for the Use of Accreditation Body Logos and for Claims of Accreditation StatusILAC-G15:2001 Guidance for Accreditation to ISO/IEC 17025ILAC-G17:2002 Introducing the Concept of Uncertainty of Measurement in Testing in Association with the

Application of the Standard ISO/IEC 17025

Secretariat Documents (S Series)ILAC-S1:2000 Guidelines for the Proposal, Drafting, Approval and Publication of ILAC DocumentsILAC-S2:1998 Rules

Procedural Documents (P Series)ILAC-P1:2000 ILAC Mutual Recognition Arrangement (Arrangement): Requirements for Evaluation of Accreditation

BodiesILAC-P2: 2000 ILAC Mutual Recognition Arrangement (Arrangement): Procedures for the Evaluation of Regional

Cooperation Bodies for the Purpose of RecognitionILAC-P3: 2002 ILAC Mutual Recognition Arrangement (Arrangement): Procedures for the Unaffi liated Bodies for the

Purpose of Recognition ILAC Mutual Recognition Arrangement (Arrangement): Terms of Reference and Composition of the

Arrangement Management Committee ILAC Mutual Recognition Arrangement (Arrangement) ILAC Mutual Recognition Arrangement (Arrangement): Policy Statement