State NIST 

Weights and Measures 

Laboratories 

Program Handbook

 

 NIST Handbook 143 

March 2003 
NIST Handbook 143 ii March 2003
NIST Handbook 143 iii March 2003

 Preface

The National Institute of Standards and Technology (NIST) manages the State Laboratory Program 

that began with the New State Standards Program established by Congress in 1965 as part of its 

continuing support to the States. This program of the NIST Weights and Measures Division (WMD) 

is designed to provide guidance, technical support, and assistance to State legal metrology 

laboratories to ensure accurate and traceable measurements from NIST to the local jurisdictions. 

The program operates through continued partnership with the State laboratories to manage numerous 

measurement-related activities. 

Significant changes have been made to the program of Recognition for the States and to this 

Program Handbook since the first edition was published in 1985. The program has incorporated 

national and international standards; although WMD does not provide formal accreditation 

according to ISO Guide 58, and although the program is operated independently from the National 

Voluntary Laboratory Accreditation Program (NVLAP), the general and technical criteria used in 

both programs are nearly identical. 

The following list shows key changes in this edition of the Handbook: 

• Information associated with the National Type Evaluation Program (NTEP) is no longer 

covered in this program handbook. 

• Parts 2 and 3 are policy and procedure information specific to WMD operations and 

Recognition process; Figure 1 is a flow chart showing the Recognition process. 

• Parts 4 and 5 substantially contain ISO/IEC 17025:1999 (previously these sections 

referenced ANSI/NCSL Z540-1-1994 (parts I and II) with NVLAP additions, WMD Notes, 

and minor editorial changes for clarity). WMD Notes added to parts 4 and 5 are additional 

policy or requirements that apply generally to all legal metrology laboratories without regard 

to Recognition level. 

• Part 6 is taken from the NVLAP Calibration Laboratories Draft Technical Guide (1994 

Draft, as incorporated in the 1996 and 1997 editions of this Handbook), but edited for this 

publication. WMD and the National Conference on Weights and Measures (NCWM) ISO 

9000 Task Force prepared the mass and volume sections and reviewed them at a special 

NVLAP workshop in December 1992 (mass criteria only); at a NVLAP workshop in 

November 1993; at all six regional metrology meetings in 1993 and 1994; and at the 1994 

NCWM meeting. Laboratories performing temperature measurements were given the 

opportunity to review the temperature section. Diane Lee (NIST) prepared the moisture 

section; it was reviewed at the Southeastern Measurement Assurance Program (SEMAP) 

regional metrology meeting in 1993. These sections have all been reviewed and updated for 

this 2003 edition. 
NIST Handbook 143 iv March 2003

• For the 1997 edition, NIST management made changes in the WMD State Laboratory 

Program. As a result, the 1997 Handbook was revised to delete references to accreditation. 

References to “accreditation” were replaced with references to “Recognition;” references to 

a “certificate of accreditation” were replaced with references to a “Certificate of 

Measurement Traceability;” and references to the WMD State Laboratory Program as an 

“accreditation program” were replaced with references to a “measurement assurance 

program.” 

Note regarding SI units: 

Appropriate SI units of measure have been used throughout this document where possible. Since 

commercial applications in the United States use units other than SI or other accepted metric units, 

this document may reference other common units in current use. 
NIST Handbook 143 v March 2003

Acknowledgments and History

This Program Handbook, first published by Henry V. Oppermann and John K. Taylor in 1985, 

documented and formalized the certification program whereby NIST Recognized the capabilities of 

State legal metrology laboratories. Prior to that time, the NIST/WMD issued “Certificates of 

Participation” to States participating in the program. In 1985, WMD started certifying laboratories 

against the criteria in Handbook 143, Program Handbook. The 1985 criteria were based on 

International Standards Organization (ISO/IEC) Guide 25 (1982), General Requirements for the 

Competence of Calibration and Testing Laboratories. 

The WMD began the process of updating this Program Handbook in 1991. Due to the many 

activities related to ISO 9000 in the United States and questions regarding how those activities 

would impact the State laboratories, ISO standards were circulated to the State laboratories in 1991. 

The National Conference of Standards Laboratories (NCSL), Total Quality Management (TQM) 

Committee also started working on the development and adoption of a single U.S. national standard 

for calibration laboratories in 1991. The NCSL TQM Committee included representatives from 

NIST, Department of Defense, Department of Energy, Nuclear Regulatory Commission, Federal 

Aviation Administration, and numerous industries. 

In 1992, the National Conference on Weights and Measures (NCWM) established an ISO 9000 Task 

Force. After review of the 1985 version of the Handbook and ISO/IEC Guide 25 to determine the 

conformance status of State laboratories, the group recommended the use of one standard in the 

United States (consistent with the NCSL position) for the accreditation of calibration laboratories to: 

1) reduce the number of redundant laboratory audits; 

2) improve measurement compatibility and acceptance of measurement results between 

laboratories in the United States and internationally; and 

3) comply with the ISO-series standards for quality. 

The NCSL “TQM Committee” became an official ANSI standards writing body (ANSI Committee 

Z 540) in 1994 and published the U.S. standard as Z540-1-1994. ANSI/NCSL Z540-1-1994 

incorporated ISO Guide 25 and Mil-Std-45662A. Since NCSL published the standard in 1994: 

1) the Department of Defense rescinded Mil-Std-45662A in favor of the Z540-1-1994 standard; 

2) the NIST National Voluntary Laboratory Accreditation Program (NVLAP) adopted and 

referenced ANSI/NCSL Z540-1-1994; 

3) the American Association for Laboratory Accreditation (A2LA), a private accrediting body, also 

adopted the standard; and 

4) the NIST/WMD incorporated the standard into Parts 5 and 6 of the 1996 and 1997 editions of 

this Handbook. Additional requirements consistent with NVLAP requirements and with the 

needs of the legal metrology system were included. 

In 1997, NIST management made the decision that NIST would operate only one formal 

accreditation program: the National Voluntary Laboratory Accreditation Program (NVLAP). 
NIST Handbook 143 vi March 2003

Therefore, all references to accreditation by WMD were changed to Recognition and WMD ceased 

issuing Certificates of Accreditation. WMD monitors the level of State compliance to this 

Handbook and other laboratory quality standards to ensure that adequate accuracy, traceability, and 

uniformity are maintained in State weights and measures laboratories. 

In 1999, ISO/IEC Guide 25 was revised and became the international standard ISO/IEC 17025. This 

2003 edition of NIST Handbook 143 incorporates revisions to the procedures and general 

requirements of the NIST Weights and Measures Division (WMD) Measurement Assurance 

Program for State Laboratory Recognition. The WMD procedures were revised to ensure continued 

consistency with international standards and guidelines, specifically those currently found in 

ISO/IEC 17025:1999, General requirements for the competence of testing and calibration 

laboratories.

The requirements in Sections 4 and 5 of this edition are nearly identical to those found in clauses 4 

and 5 of ISO/IEC 17025:1999. They must be met in order for a laboratory to be Recognized as 

competent to carry out tests and/or calibrations. Major changes from the previous edition of the 

handbook include the following: 

• In Section 4, Management requirements, there are additional or changed requirements in the 

areas of document control; requests, tenders, and contracts; purchasing; non-conforming work; 

corrective action; preventive action; and records. These additions and changes incorporate 

and/or are consistent with ISO 9001:1994 requirements. A new clause, Service to the client, 

prescribes cooperation with clients and provides guidance on such cooperation. 

• In Section 5, Technical requirements, the requirements are described in greater detail, but most 

concepts are not “new” for accredited laboratories. There is continued reference to client needs 

and greater emphasis and/or more detailed requirements on method validation; estimation of 

measurement uncertainty/traceability for testing laboratories; and provision for inclusion of 

interpretations and opinions on test reports. A sampling plan will be required where methods or 

specifications do not specify sampling procedures. 

This 2003 edition supersedes and replaces the 1997 edition of NIST Handbook 143. 
NIST Handbook 143 1 March 2003

Table of Contents 

Preface ........................................................................................................................................................iii 

Acknowledgments and History.....................................................................................................................v 

1. Program Summary ...........................................................................................................................2 

2. General Information and Operational Requirements .......................................................................4 

3. Recognition Process.......................................................................................................................10 

Table 1. Submission requirements for recognition ..........................................................17 

4. Management Requirements for Accreditation ...............................................................................18 

5. Technical Requirements for Accreditation ....................................................................................30 

6. Specific Technical Guidelines .......................................................................................................49 

Table 3. Recognition parameter summary ......................................................................50 

6.1 Technical Criteria for Dimensional Laboratories ..........................................................................51

6.2 Technical Criteria for Mass Laboratories ......................................................................................56 

Table 4. Mass calibration echelons..................................................................................56 

Table 5. Typical Ranges of Recognition for mass calibration.........................................57 

Table 6. Environmental facility guidelines for mass laboratories....................................59 

Table 7. Environmental equipment accuracy...................................................................60 

Table 8. Summary of technical criteria for mass calibration ...........................................63 

6.3 Technical Criteria for Volume Laboratories........................................................................................64 

Table 9. Typical Ranges of Recognition for volumetric calibration...............................64 

Table 10. Environmental facility guidelines for volumetric calibration..........................66 

Table 11. Environmental equipment accuracy.................................................................67 

Table 12. Summary of technical criteria for volumetric calibration................................69 

6.4 Technical Criteria for Hydrometer Laboratories..................................................................................70 

6.5 Technical Criteria for Thermometer Laboratories ...............................................................................73 

6.6 Technical Criteria for Moisture Laboratories ......................................................................................81 

Table 13. Moisture determination laboratory classifications...........................................81 

Table 14. Summary of environmental facility guidelines................................................87 

7. References......................................................................................................................................88 

8. Glossary .........................................................................................................................................89 

Appendix A. List of NIST Services...........................................................................................................94 

Appendix B. Request for Recognition, Scope of Recognition, Approved Signatories, Authorized 

Representative................................................................................................................................95 

Appendix C. Laboratory Assessment Checklist.........................................................................................96 

Appendix D. Summary of Services for Laboratory Directory.................................................................126 

Appendix E. Uncertainties Chart for Measurement Parameter................................................................130 
NIST Handbook 143 2 March 2003

1. Program Summary 

State legal metrology laboratories are custodians at the State level of measurement standards that 

serve as the basis for ensuring equity in the marketplace and as reference standards for calibration 

services for indigenous industry. As part of its program to encourage a high degree of technical and 

professional competence in such activities, the National Institute of Standards and Technology 

(NIST) Weights and Measures Division (WMD) has developed performance standards and 

formalized procedures for Recognition of State legal metrology laboratories on a voluntary basis. 

Certificates of Measurement Traceability are issued upon evaluation of the laboratory's ability to 

make reliable metrological measurements (principally mass, volume, length, and temperature). 

Recognition of State Legal Metrology Laboratories 

This Handbook describes the procedures followed in evaluating State (and a few other jurisdictional) 

legal metrology laboratories for competence. To be Recognized, a laboratory must satisfy general 

and technical requirements for each measurement area in which recognition is desired (see Appendix 

B). This program is managed by the NIST/WMD. 

The general requirements in sections 4 and 5 incorporate ISO/IEC 17025:1999 (as adopted by the 

NVLAP Calibration Laboratories Accreditation Program) and address internationally accepted 

quality practices and good management practices for calibration and testing laboratories. In addition 

to ISO/IEC 17025 and NVLAP requirements, sections 4 and 5 contain additional general 

requirements as “notes” that are specific for State legal metrology laboratories. (See Section 7. 

References.) 

The technical criteria in Section 6 amplify general criteria (ISO/IEC 17025) for each specific 

measurement parameter to be used as needed. Technical requirements of the NIST/WMD 

recognition program are nearly identical to the NVLAP guidelines published in the draft of 

NIST/NVLAP Handbook 150-2, Calibration Laboratories Technical Guide; however, WMD does 

not operate a formal accreditation program. The technical requirements include demonstration that: 

1) suitable test equipment, calibration standards, defined test procedures, and the general facilities 

necessary for good metrological services are available; and 2) that staff have a comprehensive 

understanding of calibration, measurement, and test requirements and are capable of applying them. 

Under this voluntary recognition program, laboratories appraise their compliance with the 

requirements, completing appropriate checklists that are reviewed and evaluated by NIST/WMD. 

Following review and evaluation, which includes an on-site assessment and proficiency testing, 

NIST/WMD may issue a Certificate of Measurement Traceability indicating recognized competence 

areas with defined parameters and scope of recognition; a letter describing the quality system in 

place in each laboratory is also provided. Recognition may be granted for a period up to 2 years, but 

on an annual basis each laboratory must review its status, complete an internal audit, including 
NIST Handbook 143 3 March 2003

management and quality system review, and submit the evaluation along with a statement that no 

adverse changes have taken place in order for the Recognition to remain in effect. 

Types of assistance available from the National Institute of Standards and Technology are listed in 

Appendix A. 

General

Each State legal metrology laboratory is encouraged to study this Handbook carefully and to apply 

for Recognition in all areas in which it provides measurement services. NIST/WMD reserves the 

right to deny or withdraw Recognition. In such cases, NIST/WMD will notify the State in writing of 

deficiencies, and will provide guidelines for corrective action. In the case of withdrawal, NIST will 

attempt to reach agreement with the State on the timing of the corrective action in order to keep the 

Recognition in force conditionally for legal requirements only. 
NIST Handbook 143 4 March 2003

2. General Information and Operational Requirements 

2.1 Purpose 

The NIST Enabling Act (31 Stat. 1449, 15 USC 271, Chapter 6 Weights and Measures), as modified 

by "authorities and functions pursuant to the Omnibus Trade and Competitiveness Act of 1988," 

provides the legislative authority to Recognize qualifying State weights and measures (legal 

metrology) laboratories. Authorization includes "the provision of means and methods for making 

measurements consistent with those of the national standards." Compliance with the criteria 

contained in this Handbook is the most effective means for ensuring accurate measurements 

consistent with national standards. 

2.2 Description, Quality Policy, and Objectives 

In 1965, Congress funded NIST to establish the State Standards Program to provide new standards 

of mass, volume, and length to the States, the District of Columbia, Puerto Rico, and the Virgin 

Islands to update their weights and measures laboratories and increase their measurement 

capabilities. The program also provided the laboratory equipment necessary for the States to use the 

standards in their measurement services. 

As part of the States' responsibilities in the distribution of standards and equipment, each jurisdiction 

was required to provide an acceptable laboratory facility meeting specifications established under 

the State Standards Program and to maintain acceptable staffing. The laboratory metrologist was 

required to complete training at NIST in the use of the standards and equipment. 

State Laboratory Program Quality Policy: 

It is the policy of the State Laboratory Program to help all State laboratories achieve and maintain 

Recognition and to enable State legal metrology laboratories to provide their customers accurate and 

traceable measurement services in an atmosphere of continuous quality improvement. 

As part of its continuing support to the States, NIST manages the State Laboratory Program. This is 

a program of the NIST/WMD designated to provide guidance, technical support, and assistance to 

State legal metrology laboratories to ensure accurate and traceable measurements from NIST to the 

local jurisdictions. The program operates through continued partnership with the State laboratories 

to manage numerous activities within the program. 

WMD objectives are to: 

1. support the basic level of measurement services required for legal metrology 

enforcement/oversight activities; 
NIST Handbook 143 5 March 2003

2. provide technical support for the accuracy and traceability of State legal metrology 

laboratories to the national standards through development, training, publication of, and use 

of standard procedures, protocols, and measurement assurance programs; 

3. provide and maintain the Recognition program for State legal metrology laboratories as 

evidence of continuing measurement traceability to include auditing the use and care of the 

physical standards of mass, length, and volume; and 

4. assist the States to upgrade and expand the measurement services of State legal metrology 

laboratories to satisfy the changing needs of their clients. 

2.3 Scope of Recognition 

2.3.1 Voluntary and non-contractual 

The Recognition function for State legal metrology laboratories is a voluntary, non-regulated 

program of support to the States. It provides a cost-effective means for providing evidence of 

measurement accuracy and traceability. (See sections 2.9.8 and 2.9.9.) 

2.3.2 Legal compliance requirements 

Although there are currently no Federal requirements for Recognition, some States have weights and 

measures laws that require continued formal accreditation, certification, or other form of 

Recognition by NIST as evidence of maintaining measurement traceability for primary standards 

used in the enforcement of weights and measures laws. 

2.3.3 Limitations 

The WMD Recognition program is limited in scope. It is provided for government legal metrology 

laboratories only. The NIST National Voluntary Laboratory Accreditation Program (NVLAP) offers 

accreditation services to all laboratories and is not limited in the scope of whom they may accredit. 

2.3.4 Liability

NIST Recognition does not certify individual measurements made by a State, but formally 

Recognizes that the State laboratory has traceable standards, the capability to perform reliable 

measurements, and that the metrologist has been trained in the proper procedures to provide these 

measurements. Recognition also indicates that the metrologist has submitted technical data, records, 

and documentation as specifically requested by NIST. NIST assumes no liability for the accuracy 

and traceability of individual measurement results provided by a Recognized laboratory. 

2.4 Technical Support and Assistance 

WMD offers consultative and technical support through informal and formal means to all State legal 

metrology laboratories regardless of their Recognition status. Informal assistance may be in the 

form of telephone, facsimile, e-mail, or mailed responses. Formal support and assistance are 
NIST Handbook 143 6 March 2003

available through the training program and the Regional Measurement Assurance Program (RMAP) 

of the State Laboratory Program. (See Appendix A for types of technical assistance available.) 

2.5 Confidentiality 

To the extent permitted by applicable laws, WMD will seek to ensure the confidentiality of all 

information obtained relating to the application, on-site assessment, evaluation, and Recognition of 

laboratories. Exception: see section 2.9.9 

Results of proficiency tests are generally discussed openly at annual RMAP meetings in the spirit of 

continuous improvement and teamwork. Proficiency testing may be held confidential if any 

participating State laboratory requests confidentiality of the results by writing to WMD prior to the 

beginning of each interlaboratory comparison. 

2.6 Development of Requirements 

2.6.1 Use of national and international standards wherever available

When national or international standards are available in the area of accreditation requirements for 

calibration laboratories, WMD will adopt such standards as program criteria after suitable review. 

Adoption of national or international standards, rather than independent development of standards, is 

required by Federal law whenever feasible and appropriate. 

2.6.2 Laboratory review, solicitation of comment by those affected

The technical requirements associated with the current version of Handbook 143 were developed in 

conjunction with an ISO 9000 Task Force of the National Conference on Weights and Measures. 

The technical requirements for mass and volume have been incorporated into the draft of NIST 

Handbook 150-2, Calibration Laboratories Technical Guide. Draft laboratory publications are 

reviewed by affected laboratories prior to publication. 

2.7 Documentation 

General and technical requirements for Recognition and additional documents and records to support 

the program for State laboratories are maintained and published by the NIST/WMD. 

Other publications that include the general and technical requirements for State laboratory 

Recognition, are also available: 

a) NIST Special Publication (SP) 791, State Weights and Measures Laboratories: State 

Standards Program Description and Directory 

This document contains a general program description and laboratory directory. It is updated 

periodically and is available on the NIST Internet site. 
NIST Handbook 143 7 March 2003

b) NIST Handbook 145 Handbook for the Quality Assurance of Metrological 

Measurements 

This Handbook contains laboratory procedures that are used in NIST/WMD Training Program and 

are recommended for use in State laboratories. Adequate data and evidence of measurement impact 

must be provided by the laboratory to justify deviating from documented procedures. This 

Handbook includes Good Laboratory Practices, Good Measurement Practices, and Standard 

Operating Procedures. 

c) NISTIR 5672, Advanced Mass Measurements and Measurement Assurance Program for 

State Calibration Laboratories 

This publication documents guidelines for facilities, equipment, standards, and training 

recommended for precision mass calibration and measurement control programs. It is consistent 

with the technical criteria for mass calibration and is available on the NIST Internet site. 

d) NISTIR 5802, Quality Manual Template 

This publication is a quality manual template developed as a model for State weights and Measures 

laboratories. It conforms to ISO/IEC Guide 25, ANSI/NCSL Z540-1-1994, and earlier NVLAP 

documentation requirements. It is available on the NIST Internet site. 

2.8 Records 

Records related to Recognition or accuracy and traceability of measurements and standards for each 

State are maintained in the NIST/WMD. Procedures regarding record retention are maintained in 

the WMD. These documents include, but are not limited to, the following: 

a) traceability records for primary standards; 

b) measurement control/assurance data (control charts and surveillance tests) - latest year; 

c) training; 

d) quality manuals (latest version); 

e) proficiency testing (round robin reports of the RMAPs); 

f) internal audits (including management review); and 

g) on-site assessment reports. 

Letters verifying the status of a laboratory’s Recognition level, traceability, and accompanying 

records will be provided to a State when Certificates of Measurement Traceability are issued, and 

may also be sent on behalf of the State to customers when formally requested in writing on official 

letterhead. Facsimile requests are not acceptable. 
NIST Handbook 143 8 March 2003

2.9 Rights, Duties, Responsibilities of the Recognized Laboratory 

2.9.1 Display of Certificates of Measurement Traceability

The laboratory is encouraged to post its Certificate of Measurement Traceability in the laboratory 

and may copy it for customer/client use as evidence of traceability. The copy of the certificate must 

include the Scope of Recognition (if not incorporated into the certificate). 

2.9.2 Use of Recognition or traceability status on calibration reports

The laboratory may reference its Recognition status or traceability status on reports only if the 

laboratory is Recognized in that particular measurement parameter and scope at the level specified 

on the calibration report. The laboratory must make no statements regarding Recognition for 

measurement parameters or levels of uncertainty that are not covered by the Certificate of 

Measurement Traceability and Scope. 

2.9.3 Reference to Recognition status

A laboratory may reference its Certificate of Measurement Traceability in promotional literature 

provided that it is consistent with NIST legal policy (15 CFR Ch. 11, 200.113) on the use of the 

NIST name (or NVLAP name and logo if applicable and according to NVLAP policies). This policy 

has been circulated to all State laboratories, and is available in the NIST/WMD as well as most local 

libraries. A general condition on the use of the NIST name is that it may not be used for 

endorsement purposes, but may be used to make factual statements regarding Recognition or 

traceability. 

2.9.4 Notification of change

A laboratory must advise the NIST/WMD of any changes that might affect the quality of 

measurement services it provides. This includes, but is not limited to: changes in staff, damage to 

or loss of environmental controls in its facility, damage or change of laboratory equipment used to 

provide measurement services, and damage, replacement, or recalibration of primary standards used 

to provide measurement services (including improvements as well as adverse changes). Any change 

that might adversely affect the quality of measurement results is particularly important and must be 

reported. 

2.9.5 Provide timely submissions

WMD solicits information from all laboratories each year as a reminder of the Recognition 

requirements. The laboratory must submit a report between October 1 and November 15 annually. 

This submission must include those items specifically requested, but is not limited to the items listed 

in the Recognition process. Requests for technical assistance may be made at the same time. 

Routine failure of a laboratory to provide requested material in a timely manner will result in limited 

or Conditional Recognition. 
NIST Handbook 143 9 March 2003

2.9.6 Reciprocity with other WMD-Recognized laboratories

Recognized State laboratories may have reciprocity with other Recognized or accredited State 

laboratories as a part of the voluntary registration program for service agents. Reciprocal acceptance 

of calibration reports should be limited to laboratories that have maintained Recognition with WMD 

or formal accreditation. Calibration reports from laboratories that have failed to maintain 

Recognition or formal accreditation should be refused. Information on Recognition status will be 

made available to States through Special Publication 791, Laboratory Directory and through 

individual status requests. 

2.9.7 Subcontracting

State legal metrology laboratories conduct little or no subcontracting. In the event that a laboratory 

determines that it is in its best interest to subcontract calibrations, it should subcontract only to other 

Recognized or accredited laboratories. 

2.9.8 Failure to maintain Recognition

Any laboratory that fails to maintain Recognition will be encouraged to correct deficiencies and be 

given an opportunity to submit evidence of corrective action for whatever deficiency exists. A 

laboratory that has lost Recognition status may subsequently comply with the Recognition criteria. 

Laboratories are encouraged to work closely with the NIST/WMD to reestablish Recognition as 

soon as possible. WMD will assist each laboratory as much as possible based on need and resources 

available. 

2.9.9 Notification of status 

The NIST/WMD reserves the right to notify State and Federal agencies as well as any indigenous 

industry of a State regarding Recognition or accreditation status. This is generally accomplished 

through the periodic publication of a laboratory directory and may include periodic memoranda to 

affected parties. 

2.9.10 Response to deficiencies and corrective action requests

A laboratory will have a specified amount of time to respond to deficiencies addressed through 

annual review, internal management review, NIST/WMD review, or through an on-site assessment 

conducted by NIST staff or its designated technical experts (TEs). At the end of the specified time 

period, the laboratory may be given a "conditional Recognition” detailed later in this publication. In 

the event that the laboratory fails to respond, or fails to respond adequately, it will not be 

Recognized in the particular area under question until such time as it responds or corrects 

deficiencies. The laboratory has the right to appeal WMD decisions as described later in this 

publication. 
NIST Handbook 143 10 March 2003

3. Recognition Process 

A flowchart depicting the Recognition process is shown in Figure 1. Details of this process are 

provided in this section. An overview of the Recognition process includes: 

a) an annual solicitation by WMD; 

b) technical review of submitted material (see list in Table 1); 

c) review of on-site assessment results; 

d) review of proficiency testing results; and 

e) issuance of a Certificate of Measurement Traceability, along with a scope of Recognition, and a 

letter describing the laboratory quality system. 

3.1 Request for Recognition and Fees 

Each State legal metrology laboratory, plus those of Puerto Rico, the District of Columbia, the 

Virgin Islands, Los Angeles County, and the Grain Inspection and Packers and Stockyards 

Administration (GIPSA) Master Scale Depot, may automatically renew its Recognition; however, 

the annual Request for Recognition must detail the requested Scope of Recognition. An annual 

evaluation is conducted by WMD. 

Responsibility for measurement accuracy and traceability as used in commerce is cooperatively 

shared by a number of Federal and State agencies. An excellent working partnership exists between 

the State legal metrology laboratories and NIST/WMD. The laboratories provide payment-in-kind 

through voluntary efforts for many of the activities needed to maintain the Recognition process in 

partnership with WMD. As a result of this partnership and shared responsibilities, no fees are 

charged to these laboratories to support the Recognition process. 

3.2 Annual Solicitation 

Material for Recognition and issuance of Certificates of Measurement Traceability is annually 

solicited by NIST via a detailed memorandum between August 1 and September 15. 

3.2.1 Annual submission period 

Laboratories are to submit the Request for Recognition, along with specifically requested items, each 

year between October 1 and November 15. If a laboratory fails to submit material in a timely 

manner, there is a risk that the Certificate of Measurement Traceability will not be renewed by the 

expiration date of the previous certificate. Certificates expire December 31 each year (or every 2 

years) and are renewed January 1. Material must be submitted each year for the certificate to remain 

in effect. Material submitted late will be processed as expeditiously as possible once it has been 

received by the NIST/WMD. 
NIST Handbook 143 11 March 2003

3.2.2 Information to be submitted 

The information to be submitted annually depends on the particular circumstances of a laboratory's 

Recognition and will be detailed in the solicitation memorandum. Requested information is always 

related to specific criteria as described in this Handbook. 

Generally, a Request for Recognition, a completed checklist, and all associated forms and charts 

must be submitted each time the laboratory's Certificate of Measurement Traceability is due to 

expire. A list of items is detailed in Table 1. If the Certificate of Measurement Traceability has 

lapsed, it is treated as a renewal. 

3.3 On-site Assessments (Monitoring and Requested)

Since all laboratories were established with the technical support and guidance of the NIST/WMD in 

the late 1960's or early 1970's and have been visited by WMD staff, all on-site assessments initiated 

by WMD are considered to be technical assistance visits and/or monitoring assessments. Essential 

monitoring assessments are conducted periodically, generally in conjunction with training or 

regional meetings. Additional on-site assessments may be requested by the laboratory and will be 

conducted as feasible. 

The primary objectives of on-site assessments are to: 1) ensure that the laboratories maintain 

laboratory quality by complying with documented criteria and 2) assist the laboratories to improve 

their overall operations, facilities, equipment, standards, or staff to ensure adequate accuracy and 

traceability to meet State legal requirements. On-site assessments may be conducted by NIST staff 

or by contracted Technical Experts (TEs). 

TEs use checklists, and all formal assessment reports follow the same general format to ensure 

consistency from one laboratory assessment to another. Assessments generally take between one 

and three days and are conducted to minimize disruption of normal laboratory operations. Since 

most State laboratories operate with minimal staff, as much advance notice as possible of the 

assessment date is given for scheduling purposes. 

All WMD records concerning a given laboratory are available to WMD staff, NVLAP staff (if the 

laboratory has applied to NVLAP for formal accreditation), or an assigned TE for evaluation. These 

include quality manuals, training records, RMAP attendance records, results of internal audits, 

results of round robin or other proficiency tests, control charts, NIST calibration reports, reports of 

tests, and any previous correspondence with the laboratory. During the on-site assessment, the 

assessor verifies information contained in the files through meetings with management and 

laboratory staff, by examination of facility, equipment, standards, test reports, quality documents, 

and procedures, and by observation of procedures. The assessor need not be given any information 

that violates individual privacy such as salary, medical information, or performance reviews outside 

the scope of the Recognition program. 
NIST Handbook 143 12 March 2003

Criteria Developed

Peer Review

NIST/WMD Review,

Approval, Publication

Annual Solicitation

(Aug 1 - Sept 15)

Internal Assessment,

Management Quality

Review, and Request

for Recognition

NIST/WMD Review of

Submission

NIST/WMD

Recognition

NIST/WMD On-site

Assessment

feedback to laboratory

Issue Certificate of

Meaurement Traceability,

Scope (or conditional

Recogntion and

limitations)

Yes

Withdrawal or Denial

and Laboratory

Notification

No

Corrective Action(s) or

Appeal

(or lack of submission)

Figure 1. Recognition Process.
NIST Handbook 143 13 March 2003

3.3.1 NIST staff 

On-site assessments of laboratories may or may not be conducted by NIST/WMD staff. However, 

NIST staff will prepare all final laboratory assessment reports and communicate assessment results 

to the management and staff of each laboratory. 

3.3.2 Technical experts 

TEs (may also be called regional assessors) are metrologists with technical expertise, appropriate 

auditing training and skills, and discretion, who have been selected to conduct on-site assessments 

for the State Laboratory Program. Criteria for selection are based on professional and academic 

achievement and are maintained in the NIST/WMD. 

WMD strives to ensure fairness and impartiality in its assessments. TEs are required to sign a form 

regarding laboratory confidentiality. Concerns regarding any TEs should be brought to WMD's 

attention in writing. Records are maintained for the assessments that each TE has conducted. NIST 

may provide additional training in auditing techniques for regional assessors. TEs may draft 

assessment reports; however, these reports are reviewed and finalized by WMD staff. 

3.3.3 Assessment report and invitation to respond 

Either a draft assessment report or the assessor's notes may be left with laboratory staff or 

management at the close of a formal assessment. A formal assessment report may be issued to the 

laboratory detailing deficiencies and the expected preventive or corrective action. The laboratory is 

given an opportunity to respond or appeal stated deficiencies. An assessor may or may not be fully 

aware of specific laboratory conditions and clarification may be appropriate, thus the laboratory 

response may include clarification. The laboratory is expected to correct deficiencies as soon as 

possible and to implement preventive action as a normal course of operations. The laboratory must 

submit a corrective action plan to WMD within 30 days of receiving a final report. This does not 

mean that deficiencies must be corrected within that time period; rather, it means that a plan for 

corrective action must be completed and submitted or that other steps have already been taken to 

address the deficiencies. WMD will respond to the laboratory regarding the acceptability of the 

laboratory response. 

3.3.4 Contents of assessment report 

The assessment report will contain, as a minimum, the following information: 

a) name and address of the laboratory; 

b) date of the assessment; 

c) criteria used to conduct the assessment; 

d) parameters and scope of Recognition for the assessment; 
NIST Handbook 143 14 March 2003

e) name(s) of the assessors and affiliations; 

f) name(s) of laboratory management and staff contacted during assessment; 

g) list of additional records reviewed in addition to the on-site assessment (such as the quality 

manual, training records, control charts, or round robin results maintained by WMD); 

h) references to the Program Handbook when deficiencies are identified; 

i) recommendations and preventive action for laboratory improvement and discussion related to 

cited observations; and 

j) deficiencies and corrective action required to meet program criteria and discussion related to 

cited observations. 

3.4 Proficiency Testing 

Interlaboratory comparisons (round robins) are conducted as a part of each regional measurement 

assurance program and constitute one of the primary methods used for assessment of competence. 

The other primary method is the assignment of Laboratory Auditing Program (LAP) problems upon 

the completion of each training seminar. However, on-site assessments may include demonstration 

of procedures, retest of a calibration item, or test of artifacts submitted directly to the laboratory. 

Acceptable results of proficiency tests are essential for Recognition to be granted; further 

investigation will be conducted to resolve any deficiencies. Proficiency testing results will be 

analyzed against accepted and/or standardized data analysis methods. As with on-site assessments 

and Recognition decisions, the laboratory may contact WMD regarding proficiency testing results if 

they believe an analysis was incorrect or if insufficient information was available for a complete 

evaluation. 

Proficiency testing deficiencies are defined as, but not limited to, one or more of the following: 

a) failure to meet specified proficiency testing performance requirements or objectives prescribed 

at the outset of the round robin; 

b) failure to participate in a regularly scheduled round of proficiency testing for which the 

laboratory has received instructions and/or materials; 

c) failure to submit laboratory control data as required specific to each round robin; 

d) performance as a statistically outlying laboratory in two successive rounds of proficiency testing 

or showing a general pattern of outlying results over three or more rounds; and 

e) failure to produce acceptable calibration or test results when using special artifacts whose 

properties are well-characterized and known to NIST/WMD. 

3.5 NIST Technical Evaluation 

Technical evaluation is conducted prior to awarding a Certificate of Measurement Traceability, and 

includes a full review of all available technical information regarding the laboratory. This may 

include annual submissions, control charts, quality manuals, assigned training problems, on-site 

assessment reports, results of proficiency tests, training records, attendance and participation at 
NIST Handbook 143 15 March 2003

RMAPs, formal accreditation, plus any other relevant information affecting the quality of the 

laboratory's measurement results. 

3.5.1 Review of submissions

Submissions will be reviewed and feedback provided to laboratories with the same level of 

significance as an on-site assessment. Preventive action will be recommended and corrective action 

will be required for noted deficiencies. 

3.5.1.1 New, renewal, or expansion

Any laboratory that is to receive a new certificate for January 1 must submit laboratory material 

between October 1 and November 15. Material will be reviewed by WMD between November 15 

and December 31. 

3.5.1.2 Maintenance

If a laboratory has multi-year Recognition, WMD will review material between November 15 and 

March 1 of the following year. In the event that material is not submitted during the appropriate 

time frame, WMD will review the material, as time is available, giving preference to laboratories 

without current Recognition. 

3.6 Accreditation Periods and Policy

Selection of Recognition periods is based on WMD judgment of the degree to which a laboratory 

meets criteria in this Handbook and whether the laboratory routinely submits data in a timely 

manner. While minor deficiencies may not affect a laboratory's ability to establish Recognition, they 

will result in a shorter Recognition period to encourage the necessary oversight to achieve corrective 

action. 

Each laboratory will be given every opportunity to provide input to WMD for evaluation and to 

provide feedback to WMD assessments and evaluations. Any laboratory has the right to appeal 

Recognition decisions in writing to the NIST/WMD. 

Complaints regarding the operation of the Recognition program, on-site assessments, document 

review by NIST or any NIST-assigned technical expert should be forwarded to the NIST/WMD in 

writing. 

3.6.1 Full renewal - 2 year

For those laboratories fully meeting criteria in this Handbook, a 2-year Certificate of Measurement 

Traceability will be issued; however, additional data must continue to be submitted annually for 

review as requested. Any laboratory that cannot meet the criteria in this Handbook should not apply 

for NVLAP formal accreditation. 
NIST Handbook 143 16 March 2003

3.6.2 One-year renewal 

For laboratories where WMD management and oversight are required, or when minor deficiencies 

exist, a 1-year Certificate of Measurement Traceability may be issued based on the judgement of 

WMD staff that acceptable measurements will continue to be provided to laboratory customers. 

NOTE: Until the new criteria in this Handbook are fully met (including documentation), a laboratory 

will not be issued a 2-year Certificate of Measurement Traceability. 

3.6.3 Conditional renewal

A 1-year conditional Certificate of Measurement Traceability may be granted when multiple 

deficiencies exist in the facilities, equipment, standards, staff, or overall laboratory operations, and 

that the laboratory is working to meet criteria in this Handbook. Conditional Recognition will be 

issued only to meet legal weights and measures requirements and limitations will be stated in 

writing. Conditional Recognition will be marked on the certificate. 

3.6.4 Maintenance 

If a Certificate of Measurement Traceability for a laboratory has not expired, an annual review of 

submitted data and any laboratory on-site assessments may be conducted; however, no new 

certificate will be issued since the current certificate is valid. 

3.6.5 Suspension, withdrawal, denial

In the event that circumstances change significantly during a Recognition cycle, it is the 

responsibility of the laboratory to notify WMD. Any situation that critically affects the laboratory's 

ability to provide accurate and traceable measurements may be cause for temporary suspension of 

the Certificate of Measurement Traceability until criteria are met. 

A laboratory may choose to withdraw from specific levels of Recognition based on circumstances in 

the laboratory, but may be reinstated any time it fully meets criteria in this Handbook. 

The result of an on-site assessment or of document review may include denial of Recognition. Clear 

evidence of deficiencies will be provided to the laboratory in writing along with the required 

minimum corrective action. Denial of Recognition may be modified based on the laboratory 

response or resolution of an appeal. 
NIST Handbook 143 17 March 2003

Table 1. Submission requirements for Recognition 

Reference Item Description 

Annual 

Review & 

Submission 

Changes 

or 

Renewal Updated 

Appendix B 

Request for Recognition, 

Parameters and Scope, Approved 

Signatories, Authorized 

Representative X Change 

Appendix C 

Quality Assessment Checklist and 

Management Review X 

Change; 

when 

requested 

Appendix D Summary of Services X Renewal X 

Appendix E 

Uncertainties Charts for all 

parameters X X 

Technical Assessment; Internal 

Audit Reports; Management 

Review Reports 

Note: no checklist is available X 

Laboratory Quality Manual and 

Administrative Procedures X 

NIST calibration reports for 

standards X 

Laboratory Auditing Program 

(LAP) problems assigned in 

Training Program 

X 

(completed)

Measurement control – control 

charts, surveillance tests 

When requested; 

reviewed during on-site assessments 

 Special Technical Requests 

When 

requested 
NIST Handbook 143 18 March 2003

4. Management Requirements for Accreditation1

4.1 Organization 

4.1.1 The laboratory or the organization of which it is part shall be an entity that can be held 

legally responsible. 

4.1.2 It is the responsibility of the laboratory to carry out its testing and calibration activities in 

such a way as to meet the requirements of this Handbook and to satisfy the needs of the client, the 

regulatory authorities or organizations providing Recognition. 

4.1.3 The laboratory management system shall cover work carried out in the laboratory’s 

permanent facilities, at sites away from its permanent facilities, or in associated temporary or mobile 

facilities. 

4.1.4 If the laboratory is part of an organization performing activities other than testing and/or 

calibration, the responsibilities of key personnel in the organization that have an involvement or 

influence on the testing and/or calibration activities of the laboratory shall be defined in order to 

identify potential conflicts of interest. 

NOTE 1 Where a laboratory is part of a larger organization, the organizational arrangements 

should be such that departments having conflicting interests, such as production, commercial 

marketing or financing do not adversely influence the laboratory's compliance with the requirements 

of this Handbook. 

NOTE 2 If the laboratory wishes to be Recognized as a third-party laboratory, it should be able 

to demonstrate that it is impartial and that it and its personnel are free from any undue commercial, 

financial and other pressures which might influence their technical judgment. The third-party testing 

or calibration laboratory should not engage in any activities that may endanger the trust in its 

independence of judgement and integrity in relation to its testing or calibration activities. 

4.1.5. The laboratory shall 

a) have managerial and technical personnel with the authority and resources needed to carry out 

their duties and to identify the occurrence of departures from the quality system or from the 

procedures for performing tests and/or calibrations, and to initiate actions to prevent or 

minimize such departures (see also 5.2); 

b) have arrangements to ensure that its management and personnel are free from any undue 

internal and external commercial, financial and other pressures and influences that may 

adversely affect the quality of their work; 

 

1 Section 4 substantially references the text of ISO/IEC 17025:1999, with additional NVLAP notes, WMD notes, 

and minor editorial changes for clarity. Where “this Handbook” is used in Section 4 it refers to the criteria in 

ISO/IEC 17025 as applied to this Program Handbook unless otherwise stated. NIST/WMD does not Accredit 

laboratories; however, WMD assesses State laboratories that participate in the measurement traceability program for 

conformance to these requirements.
NIST Handbook 143 19 March 2003

c) have policies and procedures to ensure the protection of its clients' confidential information and 

proprietary rights, including procedures for protecting the electronic storage and transmission of 

results; 

d) have policies and procedures to avoid involvement in any activities that would diminish 

confidence in its competence, impartiality, judgement or operational integrity; 

e) define the organization and management structure of the laboratory, its place in any parent 

organization, and the relationships between quality management, technical operations and 

support services; 

f) specify the responsibility, authority and interrelationships of all personnel who manage, 

perform or verify work affecting the quality of the tests and/or calibrations; 

g) provide adequate supervision of testing and calibration staff, including trainees, by persons 

familiar with methods and procedures, purpose of each test and/or calibration, and with the 

assessment of the test or calibration results; 

h) have technical management which has overall responsibility for the technical operations and the 

provision of the resources needed to ensure the required quality of laboratory operations; 

i) appoint a member of staff as quality manager (however named) who, irrespective of other 

duties and responsibilities, shall have defined responsibility and authority for ensuring that the 

quality system is implemented and followed at all times; the quality manager shall have direct 

access to the highest level of management at which decisions are made on laboratory policy or 

resources; and 

j) appoint deputies for key managerial personnel (see note). 

NOTE Individuals may have more than one function and it may be impractical to appoint 

deputies for each function. 

4.2 Quality System 

4.2.1 The laboratory shall establish, implement and maintain a quality system appropriate to the 

scope of its activities. The laboratory shall document its policies, systems, programs, procedures 

and instructions to the extent necessary to assure the quality of the test and/or calibration results. 

The system’s documentation shall be communicated to, understood by, available to, and 

implemented by the appropriate personnel. 

4.2.2 The laboratory’s quality system policies and objectives shall be defined in a quality manual 

(however named). The overall objectives shall be documented in a quality policy statement. The 

quality policy statement shall be issued under the authority of the chief executive. It shall include at 

least the following: 

a) the laboratory management's commitment to good professional practice and to the quality of its 

testing and calibration in servicing its clients; 

b) the management’s statement of the laboratory's standard of service; 

c) the objectives of the quality system; 
NIST Handbook 143 20 March 2003

d) a requirement that all personnel concerned with testing and calibration activities within the 

laboratory familiarize themselves with the quality documentation and implement the policies 

and procedures in their work; and 

e) the laboratory management's commitment to compliance with this Handbook. 

NOTE The quality policy statement should be concise and may include the requirement that 

tests and/or calibrations shall always be carried out in accordance with stated methods and clients' 

requirements. When the test and/or calibration laboratory is part of a larger organization, some 

quality policy elements may be in other documents. 

4.2.3 The quality manual shall include or make reference to the supporting procedures including 

technical procedures. It shall outline the structure of the documentation used in the quality system. 

4.2.4 The roles and responsibilities of technical management and the quality manager, including 

their responsibility for ensuring compliance with this Handbook, shall be defined in the quality 

manual. 

WMD NOTE The list of items in this section is not a complete list of all items that must be included 

in a quality manual. In addition to the items in this section, the laboratory’s quality manual must 

also address each of the requirements in Sections 4 and 5 of this Handbook. The NIST/WMD 

provides NISTIR 5802, Quality Manual Template for the State laboratories to use as a baseline that 

complies with the requirements of ISO/IEC Guide 25 and must be sufficiently modified to match 

specific program details and the requirements of Sections 4 and 5 of this Handbook. All 

modifications must be evaluated against these criteria. All updates must be submitted for review. 

4.3 Document Control 

4.3.1 General 

The laboratory shall establish and maintain procedures to control all documents that form part of its 

quality system (internally generated or from external sources), such as regulations, standards, other 

normative documents, test and/or calibration methods, as well as drawings, software, specifications, 

instructions and manuals. 

NOTE 1 In this context "documents" could be policy statements, procedures, specifications, 

calibration tables, charts, text books, posters, notices, memoranda, software, drawings, plans, etc.. 

These may be on various media, whether hard copy or electronic, and they may be digital, analog, 

photographic or written. 

NOTE 2 The control of data related to testing and calibration is covered in 5.4.7. The control 

of records is covered in 4.12. 
NIST Handbook 143 21 March 2003

4.3.2 Document approval and issue 

4.3.2.1 All documents issued to personnel in the laboratory as part of the quality system shall be 

reviewed and approved for use by authorized personnel prior to issue. A master list or an equivalent 

document control procedure identifying the current revision status and distribution of documents in 

the quality system shall be established and be readily available to preclude the use of invalid and/or 

obsolete documents. 

4.3.2.2 The procedure(s) adopted shall ensure 

that: 

a) authorized editions of appropriate documents are available at all locations where operations 

essential to the effective functioning of the laboratory are performed; 

b) documents are periodically reviewed and, where necessary, revised to ensure continuing 

suitability and compliance with applicable requirements; 

c) invalid or obsolete documents are promptly removed from all points of issue or use, or 

otherwise assured against unintended use; 

d) obsolete documents retained for either legal or knowledge preservation purposes are suitably 

marked. 

4.3.2.3 Quality system documents generated by the laboratory shall be uniquely identified. Such 

identification shall include the date of issue and/or revision identification, page numbering, the total 

number of pages or a mark to signify the end of the document, and the issuing authority(ies). 

4.3.3 Document changes 

4.3.3.1 Changes to documents shall be reviewed and approved by the same function that performed 

the original review unless specifically designated otherwise. The designated personnel shall have 

access to pertinent background information upon which to base their review and approval. 

4.3.3.2 Where practicable, the altered or new text shall be identified in the document or the 

appropriate attachments. 

4.3.3.3 If the laboratory's documentation control system allows for the amendment of documents by 

hand pending the reissue of the documents, the procedures and authorities for such amendments 

shall be defined. Amendments shall be clearly marked, initialed and dated. A revised document 

shall be formally reissued as soon as practicable. 

4.3.3.4 Procedures shall be established to describe how changes in documents maintained in 

computerized systems are made and controlled. 
NIST Handbook 143 22 March 2003

4.4 Review of Requests, Tenders and Contracts 

4.4.1 The laboratory shall establish and maintain procedures for the review of requests, tenders 

and contracts. The policies and procedures for these reviews leading to a contract for testing and/or 

calibration shall ensure that: 

a) the requirements, including the methods to be used, are adequately defined, documented and 

understood (see 5.4.2); 

b) the laboratory has the capability and resources to meet the requirements; and 

c) the appropriate test and/or calibration method is selected and capable of meeting the clients' 

requirements (see 5.4.2). 

Any differences between the request or tender and the contract shall be resolved before any work 

commences. Each contract shall be acceptable both to the laboratory and the client. 

NOTE 1 The request, tender and contract review should be conducted in a practical and 

efficient manner, and the effect of financial, legal and time schedule aspects should be taken into 

account. For internal clients, reviews of requests, tenders and contracts can be performed in a 

simplified way. 

NOTE 2 The review of capability should establish that the laboratory possesses the necessary 

physical, personnel and information resources, and that the laboratory's personnel have the skills and 

expertise necessary for the performance of the tests and/or calibrations in question. The review may 

also encompass results of earlier participation in interlaboratory comparisons or proficiency testing 

and/or the running of trial test or calibration programs using samples or items of known value in 

order to determine uncertainties of measurement, limits of detection, confidence limits, etc. 

NOTE 3 A contract may be any written or oral agreement to provide a client with testing 

and/or calibration services. 

4.4.2 Records of reviews, including any significant changes, shall be maintained. Records shall 

also be maintained of pertinent discussions with a client relating to the client's requirements or the 

results of the work during the period of execution of the contract. 

NOTE For review of routine and other simple tasks, the date and the identification (e.g., the 

initials) of the person in the laboratory responsible for carrying out the contracted work are 

considered adequate. For repetitive routine tasks, the review need be made only at the initial enquiry 

stage or on granting of the contract for ongoing routine work performed under a general agreement 

with the client, provided that the client's requirements remain unchanged. For new, complex or 

advanced testing and/or calibration tasks, a more comprehensive record should be maintained. 

4.4.3 The review shall also cover any work that is subcontracted by the laboratory. 

4.4.4 The client shall be informed of any deviation from the contract. 
NIST Handbook 143 23 March 2003

4.4.5 If a contract is to be amended after work has commenced, the same contract review process 

shall be repeated and any amendments shall be communicated to all affected personnel. 

4.5 Subcontracting of Tests and Calibrations 

4.5.1 When a laboratory subcontracts work whether due to unforeseen reasons (e.g., workload, 

need for further expertise or temporary incapacity) or on a continuing basis (e.g., through permanent 

subcontracting, agency or franchising arrangements), this work shall be placed with a competent 

subcontractor. A competent subcontractor is one that, for example, complies with this Handbook for 

the work in question. 

4.5.2 The laboratory shall advise the client of the arrangement in writing and, when appropriate, 

gain the approval of the client, preferably in writing. 

4.5.3 The laboratory is responsible to the client for the subcontractor’s work, except in the case 

where the client or a regulatory authority specifies which subcontractor is to be used. 

4.5.4 The laboratory shall maintain a register of all subcontractors that it uses for tests and/or 

calibrations and a record of the evidence of compliance with this Handbook for the work in question. 

4.6 Purchasing Services and Supplies 

4.6.1 The laboratory shall have a policy and procedure(s) for the selection and purchasing of 

services and supplies it uses that affect the quality of the tests and/or calibrations. Procedures shall 

exist for the purchase, reception and storage of reagents and laboratory consumable materials 

relevant for the tests and calibrations. 

4.6.2 The laboratory shall ensure that purchased supplies and reagents and consumable materials 

that affect the quality of tests and/or calibrations are not used until they have been inspected or 

otherwise verified as complying with standard specifications or requirements defined in the methods 

for the tests and/or calibrations concerned. These services and supplies used shall comply with 

specified requirements. Records of actions taken to check compliance shall be maintained. 

4.6.3 Purchasing documents for items affecting the quality of laboratory output shall contain data 

describing the services and supplies ordered. These purchasing documents shall be reviewed and 

approved for technical content prior to release. 

NOTE The description may include type, class, grade, precise identification, specifications, 

drawings, inspection instructions, other technical data including approval of test results, the quality 

required and the quality system standard under which they were made. 
NIST Handbook 143 24 March 2003

4.6.4 The laboratory shall evaluate suppliers of critical consumables, supplies and services which 

affect the quality of testing and calibration, and shall maintain records of these evaluations and list 

those approved. 

4.7 Service to the Client 

The laboratory shall afford clients or their representatives cooperation to clarify the client's request 

and to monitor the laboratory’s performance in relation to the work performed, provided that the 

laboratory ensures confidentiality to other clients. 

NOTE 1 Such cooperation may include: 

a) providing the client or the client's representative reasonable access to relevant areas of the 

laboratory for the witnessing of tests and/or calibrations performed for the client; and 

b) preparation, packaging, and dispatch of test and/or calibration items needed by the client for 

verification purposes. 

NOTE 2 Clients value the maintenance of good communication, advice and guidance in 

technical matters, and opinions and interpretations based on results. Communication with the client, 

especially in large assignments, should be maintained throughout the work. The laboratory should 

inform the client of any delays or major deviations in the performance of the tests and/or 

calibrations. 

NOTE 3 Laboratories are encouraged to obtain other feedback, both positive and negative, 

from their clients (e.g., client surveys). The feedback should be used to improve the quality system, 

testing and calibration activities and client service. 

4.8 Complaints 

The laboratory shall have a policy and procedure for the resolution of complaints received from 

clients or other parties. Records shall be maintained of all complaints and of the investigations and 

corrective actions taken by the laboratory (see also 4.10). 

4.9 Control of Non-conforming Testing and/or Calibration Work 

4.9.1 The laboratory shall have a policy and procedures that shall be implemented when any aspect 

of its testing and/or calibration work, or the results of this work, do not conform to its own 

procedures or the agreed requirements of the client. The policy and procedures shall ensure that: 

a) the responsibilities and authorities for the management of non-conforming work are designated 

and actions (including halting of work and withholding of test reports and calibration 

certificates, as necessary) are defined and taken when non-conforming work is identified; 

b) an evaluation of the significance of the non-conforming work is made; 
NIST Handbook 143 25 March 2003

c) corrective actions are taken immediately, together with any decision about the acceptability of 

the non-conforming work; 

d) where necessary, the client is notified and work is recalled; and 

e) the responsibility for authorizing the resumption of work is defined. 

NOTE Identification of non-conforming work or problems with the quality system or with testing 

and/or calibration activities can occur at various places within the quality system and technical 

operations. Examples are customer complaints, quality control, instrument calibration, checking of 

consumable materials, staff observations or supervision, test report and calibration certificate 

checking, management reviews and internal or external audits. 

4.9.2 Where the evaluation indicates that the non-conforming work could recur or that there is 

doubt about the compliance of the laboratory's operations with its own policies and 

procedures, the corrective action procedures given in 4.10 shall be promptly followed. 

4.10 Corrective Action 

4.10.1 General 

The laboratory shall establish a policy and procedure and shall designate appropriate authorities for 

implementing corrective action when non-conforming work or departures from the policies and 

procedures in the quality system or technical operations have been identified. 

NOTE A problem with the quality system or with the technical operations of the laboratory 

may be identified through a variety of activities, such as control of non-conforming work, internal or 

external audits, management reviews, feedback from clients or staff observations. 

4.10.2 Cause analysis 

The procedure for corrective action shall start with an investigation to determine the root cause(s) of 

the problem. 

NOTE Cause analysis is the key and sometimes the most difficult part in the corrective action 

procedure. Often the root cause is not obvious and thus a careful analysis of all potential causes of 

the problem is required. Potential causes could include client requirements, the samples, sample 

specifications, methods and procedures, staff skills and training, consumables, or equipment and its 

calibration. 

4.10.3 Selection and implementation of corrective actions 

Where corrective action is needed, the laboratory shall identify potential corrective actions. It shall 

select and implement the action(s) most likely to eliminate the problem and to prevent recurrence. 

Corrective actions shall be to a degree appropriate to the magnitude and the risk of the problem. 
NIST Handbook 143 26 March 2003

The laboratory shall document and implement any required changes resulting from corrective action 

investigations. 

4.10.4 Monitoring of corrective actions 

The laboratory shall monitor the results to ensure that the corrective actions taken have been 

effective. 

4.10.5 Additional audits 

Where the identification of non-conformances or departures casts doubts on the laboratory's 

compliance with its own policies and procedures, or on its compliance with this Handbook, the 

laboratory shall ensure that the appropriate areas of activity are audited in accordance with 4.13 as 

soon as possible. 

NOTE Such additional audits often follow the implementation of the corrective actions to 

confirm their effectiveness. An additional audit should be necessary only when a serious issue or 

risk to the business is identified. 

4.11 Preventive Action 

4.11.1 Needed improvements and potential sources of non-conformances, either technical or 

concerning the quality system, shall be identified. If preventive action is required, action plans shall 

be developed, implemented and monitored to reduce the likelihood of the occurrence of such nonconformances and to take advantage of the opportunities for improvement. 

4.11.2 Procedures for preventive actions shall include the initiation of such actions and application 

of controls to ensure that they are effective. 

NOTE 1 Preventive action is a proactive process to identify opportunities for improvement 

rather than a reaction to the identification of problems or complaints. 

NOTE 2 Apart from the review of the operational procedures, the preventive action might 

involve analysis of data, including trend and risk analyses and proficiency testing results. 

4.12 Control of Records 

4.12.1 General 

4.12.1.1 The laboratory shall establish and maintain procedures for identification, collection, 

indexing, access, filing, storage, maintenance and disposal of quality and technical records. Quality 

records shall include reports from internal audits and management reviews as well as records of 

corrective and preventive actions. 
NIST Handbook 143 27 March 2003

4.12.1.2 All records shall be legible and shall be stored and retained in such a way that they 

are readily retrievable in facilities that provide a suitable environment to prevent damage or 

deterioration and to prevent loss. Retention times of records shall be established. 

NOTE Records may be in any media, such as hard copy or electronic media. 

4.12.1.3 All records shall be held secure and in confidence. 

4.12.1.4 The laboratory shall have procedures to protect and back up records stored 

electronically and to prevent unauthorized access to or amendment of these records. 

4.12.2 Technical Records 

4.12.2.1 The laboratory shall retain records of original observations, derived data and 

sufficient information to establish an audit trail, calibration records, staff records and a copy of each 

test report or calibration certificate issued, for a defined period. The records for each test or 

calibration shall contain sufficient information to facilitate, if possible, identification of factors 

affecting the uncertainty and to enable the test or calibration to be repeated under conditions as close 

as possible to the original. The records shall include the identity of personnel responsible for the 

sampling, performance of each test and/or calibration and checking of results. 

NOTE 1 In certain fields it may be impossible or impracticable to retain records of all original 

observations. 

NOTE 2 Technical records are accumulations of data (see 5.4.7) and information which result 

from carrying out tests and/or calibrations and which indicate whether specified quality or process 

parameters are achieved. They may include forms, contracts, work sheets, work books, check 

sheets, work notes, control graphs, external and internal test reports and calibration certificates, 

clients' notes, papers and feedback. 

4.12.2.2 Observations, data and calculations shall be recorded at the time they are made and 

shall be identifiable to the specific task. 

4.12.2.3 When mistakes occur in records, each mistake shall be crossed out, not erased, made 

illegible or deleted, and the correct value entered alongside. All such alterations to records shall be 

signed or initialed by the person making the correction. In the case of records stored electronically, 

equivalent measures shall be taken to avoid loss or change of original data. 

4.13 Internal Audits 

4.13.1 The laboratory shall periodically, and in accordance with a predetermined schedule and 

procedure, conduct internal audits of its activities to verify that its operations continue to comply 

with the requirements of the quality system and this Handbook. The internal audit program shall 

address all elements of the quality system, including the testing and/or calibration activities. It is the 

responsibility of the quality manager to plan and organize audits as required by the schedule and 
NIST Handbook 143 28 March 2003

requested by management. Such audits will be carried out by trained and qualified personnel who 

are, wherever resources permit, independent of the activity to be audited. 

NOTE The cycle for internal auditing should normally be completed in one year. 

4.13.2 When audit findings cast doubt on the effectiveness of the operations or on the correctness or 

validity of the laboratory's test or calibration results, the laboratory shall take timely corrective 

action, and shall notify clients in writing if investigations show that the laboratory results may have 

been affected. 

4.13.3 The area of activity audited, the audit findings and corrective actions that arise from them 

shall be recorded. 

4.13.4 Follow-up audit activities shall verify and record the implementation and effectiveness of the 

corrective action taken. 

4.14 Management Reviews 

4.14.1 In accordance with a predetermined schedule and procedure, the laboratory’s executive 

management shall periodically conduct a review of the laboratory's quality system and testing and/or 

calibration activities to ensure their continuing suitability and effectiveness, and to introduce 

necessary changes or improvements. The review shall take account of: 

— the suitability of policies and procedures; 

— reports from managerial and supervisory personnel; 

— the outcome of recent internal audits (see 4.13); 

— corrective and preventive actions; 

— assessments by external bodies; 

— the results of interlaboratory comparisons or proficiency tests; 

— changes in the volume and type of the work; 

— client feedback; 

— complaints; and 

— other relevant factors, such as quality control activities, resources and staff training. 

NOTE 1 A typical period for conducting a management review is once every 12 months. 

NOTE 2 Results should feed into the laboratory planning system and should include the goals, 

objectives and action plans for the coming year. 
NIST Handbook 143 29 March 2003

NOTE 3 A management review includes consideration of related subjects at regular 

management meetings. 

4.14.2 Findings from management reviews and the actions that arise from them shall be 

recorded. The management shall ensure that those actions are carried out within an appropriate 

and agreed timescale. 
NIST Handbook 143 30 March 2003

5. Technical Requirements for Accreditation2

5.1 General 

5.1.1 Many factors determine the correctness and reliability of the tests and/or calibrations 

performed by a laboratory. These factors include contributions from: 

— human factors (5.2); 

— accommodation and environmental conditions (5.3); 

— test and calibration methods and method validation (5.4); 

— equipment (5.5); 

— measurement traceability (5.6); 

— sampling (5.7); and 

— the handling of test and calibration items (5.8). 

5.1.2 The extent to which the factors contribute to the total uncertainty of measurement differs 

considerably between (types of) tests and between (types of) calibrations. The laboratory shall take 

account of these factors in developing test and calibration methods and procedures, in the training 

and qualification of personnel, and in the selection and calibration of the equipment it uses. 

5.2 Personnel 

5.2.1 The laboratory management shall ensure the competence of all who operate specific 

equipment, perform tests and/or calibrations, evaluate results, and sign test reports and calibration 

certificates. When using staff who are undergoing training, appropriate supervision shall be 

provided. Personnel performing specific tasks shall be qualified on the basis of appropriate 

education, training, experience and/or demonstrated skills, as required. 

NOTE 1 In some technical areas (e.g., nondestructive testing) it may be required that the 

personnel performing certain tasks hold personnel certification. The laboratory is responsible for 

fulfilling specified personnel certification requirements. The requirements for personnel 

certification might be regulatory, included in the standards for the specific technical field, or 

required by the client. 

NOTE 2 The personnel responsible for the opinions and interpretation included in test reports 

should, in addition to the appropriate qualifications, training, experience and satisfactory knowledge 

of the testing carried out, also have: 

— relevant knowledge of the technology used for the manufacturing of the items, materials, 

 

2 Section 5 substantially references the text of ISO/IEC 17025:1999, with additional NVLAP notes, WMD notes, 

and minor editorial changes for clarity. Where “this Handbook” is used in Section 4 it refers to the criteria in 

ISO/IEC 17025 as applied to this Program Handbook unless otherwise stated. NIST/WMD does not Accredit 

laboratories; however, WMD assesses State laboratories that participate in the measurement traceability program for 

conformance to these requirements. 
NIST Handbook 143 31 March 2003

products, etc. tested, or the way they are used or intended to be used, and of the defects or 

degradations which may occur during or in service; 

— knowledge of the general requirements expressed in the legislation and standards; and 

— an understanding of the significance of deviations found with regard to the normal use of the 

items, materials, products, etc., concerned. 

5.2.2 The management of the laboratory shall formulate the goals with respect to the education, 

training and skills of the laboratory personnel. The laboratory shall have a policy and procedures for 

identifying training needs and providing training of personnel. The training program shall be 

relevant to the present and anticipated tasks of the laboratory. 

5.2.3 The laboratory shall use personnel who are employed by, or under contract to, the laboratory. 

Where contracted and additional technical and key support personnel are used, the laboratory shall 

ensure that such personnel are supervised and competent and that they work in accordance with the 

laboratory's quality system. 

5.2.4 The laboratory shall maintain current job descriptions for managerial, technical and key 

support personnel involved in tests and/or calibrations. 

NOTE Job descriptions can be defined in many ways. As a minimum, the following should be 

defined: 

— the responsibilities with respect to performing tests and/or calibrations; 

— the responsibilities with respect to the planning of tests and/or calibrations and evaluation of 

results; 

— the responsibilities for reporting opinions and interpretations; 

— the responsibilities with respect to method modification and development and validation of new 

methods; 

— expertise and experience required; 

— qualifications and training programs; and 

— managerial duties. 

5.2.5 The management shall authorize specific personnel to perform particular types of sampling, 

test and/or calibration, to issue test reports and calibration certificates, to give opinions and 

interpretations and to operate particular types of equipment. The laboratory shall maintain records 

of the relevant authorization(s), competence, educational and professional qualifications, training, 

skills and experience of all technical personnel, including contracted personnel. This information 

shall be readily available and shall include the date on which authorization and/or competence is 

confirmed. 

WMD NOTE 1: This requirement also applies to Approved Signatories. 
NIST Handbook 143 32 March 2003

WMD NOTE 2: The NIST/WMD provides training to State legal metrology laboratories. State 

metrologists are required to complete the appropriate level of training as indicated in Table 2 , for 

the laboratory to be Recognized at designated levels. Information regarding the training program is 

maintained in the WMD. 

5.3 Accommodation and Environmental Conditions 

5.3.1 Laboratory facilities for testing and/or calibration, including but not limited to energy 

sources, lighting and environmental conditions, shall be such as to facilitate correct performance of 

the tests and/or calibrations. 

The laboratory shall ensure that the environmental conditions do not invalidate the results or 

adversely affect the required quality of any measurement. Particular care shall be taken when 

sampling and tests and/or calibrations are undertaken at sites other than a permanent laboratory 

facility. The technical requirements for accommodation and environmental conditions that can 

affect the results of tests and calibrations shall be documented. 

5.3.2 The laboratory shall monitor, control and record environmental conditions as required by the 

relevant specifications, methods and procedures or where they influence the quality of the results. 

Due attention shall be paid, for example, to biological sterility, dust, electromagnetic disturbances, 

radiation, humidity, electrical supply, temperature, and sound and vibration levels, as appropriate to 

the technical activities concerned. Tests and calibrations shall be stopped when the environmental 

conditions jeopardize the results of the tests and/or calibrations. 

5.3.3 There shall be effective separation between neighboring areas in which there are 

incompatible activities. Measures shall be taken to prevent cross-contamination. 

5.3.4 Access to and use of areas affecting the quality of the tests and/or calibrations shall be 

controlled. The laboratory shall determine the extent of control based on its particular 

circumstances. 

5.3.5 Measures shall be taken to ensure good housekeeping in the laboratory. Special procedures 

shall be prepared where necessary. 

5.4 Test and Calibration Methods and Method Validation 

5.4.1 General 

The laboratory shall use appropriate methods and procedures for all tests and/or calibrations within 

its scope. These include sampling, handling, transport, storage and preparation of items to be tested 

and/or calibrated, and, where appropriate, an estimation of the measurement uncertainty as well as 

statistical techniques for analysis of test and/or calibration data. 

The laboratory shall have instructions on the use and operation of all relevant equipment, and on the 

handling and preparation of items for testing and/or calibration, or both, where the absence of such 
NIST Handbook 143 33 March 2003

instructions could jeopardize the results of tests and/or calibrations. All instructions, standards, 

manuals and reference data relevant to the work of the laboratory shall be kept up to date and shall 

be made readily available to personnel (see 4.3). Deviation from test and calibration methods shall 

occur only if the deviation has been documented, technically justified, authorized, and accepted by 

the client. 

NOTE International, regional or national standards or other recognized specifications that 

contain sufficient and concise information on how to perform the tests and/or calibrations do not 

need to be supplemented or rewritten as internal procedures if these standards are written in a way 

that they can be used as published by the operating staff in a laboratory. It may be necessary to 

provide additional documentation for optional steps in the method or additional details. 

WMD NOTE The NIST/WMD maintains NIST Handbook 145, Handbook for the Quality 

Assurance of Metrological Measurements. States must reference this Handbook and use it for all 

applicable measurement procedures unless data or other evidence is available to support acceptable 

results using another procedure. Other procedures must be submitted to WMD for review and 

approval by the NIST/WMD. Use of uniform procedures is critical for maintaining the integrity of 

the legal measurement system. 

5.4.2 Selection of methods

The laboratory shall use test and/or calibration methods, including methods for sampling, which 

meet the needs of the client and which are appropriate for the tests and/or calibrations it undertakes. 

Methods published in international, regional or national standards shall preferably be used. The 

laboratory shall ensure that it uses the latest valid edition of a standard unless it is not appropriate or 

possible to do so. When necessary, the standard shall be supplemented with additional details to 

ensure consistent application. 

When the client does not specify the method to be used, the laboratory shall select appropriate 

methods that have been published either in international, regional or national standards, or by 

reputable technical organizations, or in relevant scientific texts or journals, or as specified by the 

manufacturer of the equipment. Laboratory-developed methods or methods adopted by the 

laboratory may also be used if they are appropriate for the intended use and if they are validated. 

The client shall be informed as to the method chosen. The laboratory shall confirm that it can 

properly operate standard methods before introducing the tests or calibrations. If the standard 

method changes, the confirmation shall be repeated. 

The laboratory shall inform the client when the method proposed by the client is considered to be 

inappropriate or out of date. 
NIST Handbook 143 34 March 2003

5.4.3 Laboratory-developed methods 

The introduction of test and calibration methods developed by the laboratory for its own use shall be 

a planned activity and shall be assigned to qualified personnel equipped with adequate resources. 

Plans shall be updated as development proceeds and effective communication amongst all personnel 

involved shall be ensured. 

5.4.4 Non-standard methods 

When it is necessary to use methods not covered by standard methods, these shall be subject to 

agreement with the client and shall include a clear specification of the client's requirements and the 

purpose of the test and/or calibration. The method developed shall have been validated 

appropriately before use. 

NOTE For new test and/or calibration methods, procedures should be developed before tests 

and/or calibrations are performed and should contain at least the following information: 

a) appropriate identification; 

b) scope; 

c) description of the type of item to be tested or calibrated; 

d) parameters or quantities and ranges to be determined; 

e) apparatus and equipment, including technical performance requirements; 

f) reference standards and reference materials required; 

g) environmental conditions required and any stabilization period needed; 

h) description of the procedure, including: 

— affixing of identification marks, handling, transporting, storing and preparation of items, 

— checks to be made before the work is started, 

— checks that the equipment is working properly and, where required, calibration and 

adjustment of the equipment before each use, 

— the method of recording the observations and results, and 

— any safety measures to be observed; 

i) criteria and/or requirements for approval/rejection; 

j) data to be recorded and method of analysis and presentation; and 

k) the uncertainty or the procedure for estimating uncertainty. 

5.4.5 Validation of methods 

5.4.5.1 Validation is the confirmation by examination and the provision of objective evidence that 

the particular requirements for a specific intended use are fulfilled. 

5.4.5.2 The laboratory shall validate non-standard methods, laboratory-designed/developed methods, 

standard methods used outside their intended scope, and amplifications and modifications of 

standard methods to confirm that the methods are fit for the intended use. The validation shall be as 

extensive as necessary to meet the needs of the given application or field of application. The 
NIST Handbook 143 35 March 2003

laboratory shall record the results obtained, the procedure used for the validation, and a statement as 

to whether the method is fit for the intended use. 

NOTE 1 Validation may include procedures for sampling, handling and transportation. 

NOTE 2 The techniques used for the determination of the performance of a method should be 

one of, or a combination of, the following: 

— calibration using reference standards or reference materials; 

— comparison of results achieved with other methods; 

— interlaboratory comparisons; 

— systematic assessment of the factors influencing the result; and 

— assessment of the uncertainty of the results based on scientific understanding of the theoretical 

principles of the method and practical experience. 

NOTE 3 For changes in the validated non-standard methods, their influence should be 

documented and, if appropriate, another validation should be carried out. 

5.4.5.3 The range and accuracy of the values obtainable from validated methods (e.g., the 

uncertainty of the results, detection limit, selectivity of the method, linearity, limit of repeatability 

and/or reproducibility, robustness against external influences and/or cross-sensitivity against 

interference from the matrix of the sample/test object), as assessed for the intended use, shall be 

relevant to the client needs. 

NOTE 1 Validation includes specification of the requirements, determination of the 

characteristics of the methods, a check that the requirements can be fulfilled by using the method, 

and a statement on the validity. 

NOTE 2 As method development proceeds, regular review should be carried out to verify that 

the client needs are still being fulfilled. Any change in requirements requiring modifications to the 

development plan should be approved and authorized. 

NOTE 3 Validation is always a balance between costs, risks and technical possibilities. There 

are many cases in which the range and uncertainty of the values (e.g., accuracy, detection limit, 

selectivity, linearity, repeatability, reproducibility, robustness and cross-sensitivity) can only be 

given in a simplified way due to lack of information. 

5.4.6 Estimation of uncertainty of measurement 

5.4.6.1 A calibration laboratory, or a testing laboratory performing its own calibrations, shall have 

and shall apply a procedure to estimate the uncertainty of measurement for all calibrations and types 

of calibrations. 

5.4.6.2 Testing laboratories shall have and shall apply procedures for estimating uncertainty of 

measurement. In certain cases the nature of the test method may preclude rigorous, metrologically 
NIST Handbook 143 36 March 2003

and statistically valid, calculation of uncertainty of measurement. In these cases the laboratory shall 

at least attempt to identify all the components of uncertainty and make a reasonable estimation, and 

shall ensure that the form of reporting of the result does not give a wrong impression of the 

uncertainty. Reasonable estimation shall be based on knowledge of the performance of the method 

and on the measurement scope and shall make use of, for example, previous experience and 

validation data. 

NOTE 1 The degree of rigor needed in an estimation of uncertainty of measurement depends 

on factors such as: 

— the requirements of the test method; 

— the requirements of the client; and 

— the existence of narrow limits on which decisions on conformance to a specification are based. 

NOTE 2 In those cases where a well-recognized test method specifies limits to the values of 

the major sources of uncertainty of measurement and specifies the form of presentation of calculated 

results, the laboratory is considered to have satisfied this clause by following the test method and 

reporting instructions (see 5.10). 

5.4.6.3 When estimating the uncertainty of measurement, all uncertainty components which are of 

importance in the given situation shall be taken into account using appropriate methods of analysis. 

NOTE 1 Sources contributing to the uncertainty include, but are not necessarily limited to, the 

reference standards and reference materials used, methods and equipment used, environmental 

conditions, properties and condition of the item being tested or calibrated, and the operator. 

NOTE 2 The predicted long-term behavior of the tested and/or calibrated item is not normally 

taken into account when estimating the measurement uncertainty. 

NOTE 3 For further information, see ISO 5725 and the Guide to the Expression of Uncertainty 

in Measurement (see 1.4). 

WMD NOTE ANSI/NCSL Z540-2-1997 and NIST Technical Note 1297, 1994 edition, are 

considered to be equivalent to the Guide to the Expression of Uncertainty in Measurement (GUM). 

5.4.7 Control of data 

5.4.7.1 Calculations and data transfers shall be subject to appropriate checks in a systematic manner. 

5.4.7.2 When computers or automated equipment are used for the acquisition, processing, recording, 

reporting, storage or retrieval of test or calibration data, the laboratory shall ensure that: 

a) computer software developed by the user is documented in sufficient detail and is suitably 

validated as being adequate for use; 
NIST Handbook 143 37 March 2003

b) procedures are established and implemented for protecting the data; such procedures shall 

include, but not be limited to, integrity and confidentiality of data entry or collection, data 

storage, data transmission and data processing; and 

c) computers and automated equipment are maintained to ensure proper functioning and are 

provided with the environmental and operating conditions necessary to maintain the integrity of 

test and calibration data. 

NOTE Commercial off-the-shelf software (e.g., word processing, database and statistical 

programs) in general use within their designed application range may be considered to be 

sufficiently validated. However, laboratory software configuration/modifications should be 

validated as in 5.4.7.2a). 

5.5 Equipment 

5.5.1 The laboratory shall be furnished with all items of sampling, measurement and test 

equipment required for the correct performance of the tests and/or calibrations (including sampling, 

preparation of test and/or calibration items, processing and analysis of test and/or calibration data). 

In those cases where the laboratory needs to use equipment outside its permanent control, it shall 

ensure that the requirements of this Handbook are met. 

5.5.2 Equipment and its software used for testing, calibration and sampling shall be capable of 

achieving the accuracy required and shall comply with specifications relevant to the tests and/or 

calibrations concerned. Calibration programs shall be established for key quantities or values of the 

instruments where these properties have a significant effect on the results. Before being placed into 

service, equipment (including that used for sampling) shall be calibrated or checked to establish that 

it meets the laboratory's specification requirements and complies with the relevant standard 

specifications. It shall be checked and/or calibrated before use (see 5.6). 

5.5.3 Equipment shall be operated by authorized personnel. Up-to-date instructions on the use and 

maintenance of equipment (including any relevant manuals provided by the manufacturer of the 

equipment) shall be readily available for use by the appropriate laboratory personnel. 

5.5.4 Each item of equipment and its software used for testing and calibration and significant to the 

result shall, when practicable, be uniquely identified. 

5.5.5 Records shall be maintained of each item of equipment and its software significant to the 

tests and/or calibrations performed. The records shall include at least the following: 

a) the identity of the item of equipment and its software; 

b) the manufacturer's name, type identification, and serial number or other unique identification; 

c) checks that equipment complies with the specification (see 5.5.2); 

d) the current location, where appropriate; 

e) the manufacturer's instructions, if available, or reference to their location; 

f) dates, results and copies of reports and certificates of all calibrations, adjustments, acceptance 

criteria, and the due date of next calibration; 
NIST Handbook 143 38 March 2003

g) the maintenance plan, where appropriate, and maintenance carried out to date; and 

h) any damage, malfunction, modification or repair to the equipment. 

5.5.6 The laboratory shall have procedures for safe handling, transport, storage, use and planned 

maintenance of measuring equipment to ensure proper functioning and in order to prevent 

contamination or deterioration. 

NOTE Additional procedures may be necessary when measuring equipment is used outside 

the permanent laboratory for tests, calibrations or sampling. 

5.5.7 Equipment that has been subjected to overloading or mishandling, gives suspect results, or 

has been shown to be defective or outside specified limits, shall be taken out of service. It shall be 

isolated to prevent its use or clearly labeled or marked as being out of service until it has been 

repaired and shown by calibration or test to perform correctly. The laboratory shall examine the 

effect of the defect or departure from specified limits on previous tests and/or calibrations and shall 

institute the "Control of non-conforming work" procedure (see 4.9). 

5.5.8 Whenever practicable, all equipment under the control of the laboratory and requiring 

calibration shall be labeled, coded or otherwise identified to indicate the status of calibration, 

including the date when last calibrated and the date or expiration criteria when recalibration is due. 

5.5.9 When, for whatever reason, equipment goes outside the direct control of the laboratory, the 

laboratory shall ensure that the function and calibration status of the equipment are checked and 

shown to be satisfactory before the equipment is returned to service. 

5.5.10 When intermediate checks are needed to maintain confidence in the calibration status of the 

equipment, these checks shall be carried out according to a defined procedure. 

5.5.11 Where calibrations give rise to a set of correction factors, the laboratory shall have 

procedures to ensure that copies (e.g., in computer software) are correctly updated. 

5.5.12 Test and calibration equipment, including both hardware and software, shall be safeguarded 

from adjustments which would invalidate the test and/or calibration results. 

WMD NOTE The quality manual template contains a chart to list equipment and its current 

performance evaluation. This information will be requested during on-site assessments, and the 

chart may be requested annually for review with measurement control documents. 
NIST Handbook 143 39 March 2003

5.6 Measurement Traceability 

5.6.1 General 

All equipment used for tests and/or calibrations, including equipment for subsidiary measurements 

(e.g., for environmental conditions) having a significant effect on the accuracy or validity of the 

result of the test, calibration or sampling shall be calibrated before being put into service. The 

laboratory shall have an established program and procedure for the calibration of its equipment. 

NOTE Such a program should include a system for selecting, using, calibrating, checking, 

controlling and maintaining measurement standards, reference materials used as measurement 

standards, and measuring and test equipment used to perform tests and calibrations. 

5.6.2 Specific requirements 

5.6.2.1 Calibration 

5.6.2.1.1 For calibration laboratories, the program for calibration of equipment shall be 

designed and operated so as to ensure that calibrations and measurements made by the laboratory are 

traceable to the International System of Units (SI) (Système international d'unités). 

A calibration laboratory establishes traceability of its own measurement standards and measuring 

instruments to the SI by means of an unbroken chain of calibrations or comparisons linking them to 

relevant primary standards of the SI units of measurement. The link to SI units may be achieved by 

reference to national measurement standards. National measurement standards may be primary 

standards, which are primary realizations of the SI units or agreed representations of SI units based 

on fundamental physical constants, or they may be secondary standards which are standards 

calibrated by another national metrology institute. When using external calibration services, 

traceability of measurement shall be assured by the use of calibration services from laboratories that 

can demonstrate competence, measurement capability and traceability. The calibration certificates 

issued by these laboratories shall contain the measurement results, including the measurement 

uncertainty and/or a statement of compliance with an identified metrological specification (see also 

5.10.4.2). 

NOTE 1 Calibration laboratories fulfilling the requirements of this Handbook are considered 

to be competent. A calibration certificate bearing an accreditation body logo from a calibration 

laboratory accredited to this Handbook, for the calibration concerned, is sufficient evidence of 

traceability of the calibration data reported. 

NOTE 2 Traceability to SI units of measurement may be achieved by reference to an 

appropriate primary standard (see VIM:1993, 6.4) or by reference to a natural constant, the value of 

which in terms of the relevant SI unit is known and recommended by the General Conference of 

Weights and Measures (CGPM) and the International Committee for Weights and Measures (CIPM). 

NOTE 3 Calibration laboratories that maintain their own primary standard or representation of 
NIST Handbook 143 40 March 2003

SI units based on fundamental physical constants can claim traceability to the SI system only after 

these standards have been compared, directly or indirectly, with other similar standards of a national 

metrology institute. 

NOTE 4 The term "identified metrological specification" means that it must be clear from the 

calibration certificate which specification the measurements have been compared with, by including 

the specification or by giving an unambiguous reference to the specification. 

NOTE 5 When the terms "international standard" or "national standard" are used in connection 

with traceability, it is assumed that these standards fulfill the properties of primary standards for the 

realization of SI units. 

NOTE 6 Traceability to national measurement standards does not necessarily require the use of 

the national metrology institute of the country in which the laboratory is located. 

NOTE 7 If a calibration laboratory wishes or needs to obtain traceability from a national 

metrology institute other than in its own country, this laboratory should select a national metrology 

institute that actively participates in the activities of BIPM either directly or through regional groups. 

NOTE 8 The unbroken chain of calibrations or comparisons may be achieved in several steps 

carried out by different laboratories that can demonstrate traceability. 

5.6.2.1.2 Some calibrations cannot currently be made strictly in SI units. In these cases, 

calibration shall provide confidence in measurements by establishing traceability to appropriate 

measurement standards, such as: 

— the use of certified reference materials provided by a competent supplier to give a reliable 

physical or chemical characterization of a material; and 

— the use of specified methods and/or consensus standards that are clearly described and agreed 

by all parties concerned. 

Participation in a suitable program of interlaboratory comparisons is required whenever possible. 

5.6.2.2 Testing 

5.6.2.2.1 For testing laboratories, the requirements given in 5.6.2.1 apply for measuring and 

test equipment with measuring functions used, unless it has been established that the associated 

contribution from the calibration contributes little to the total uncertainty of the test result. When 

this situation arises, the laboratory shall ensure that the equipment used can provide the uncertainty 

of measurement needed. 

NOTE The extent to which the requirements in 5.6.2.1 should be followed depends on the 

relative contribution of the calibration uncertainty to the total uncertainty. If calibration is the 

dominant factor, the requirements should be strictly followed. 
NIST Handbook 143 41 March 2003

5.6.2.2.2 Where traceability of measurements to SI units is not possible and/or not relevant, the 

same requirements for traceability to, for example, certified reference materials, agreed methods 

and/or consensus standards, are required as for calibration laboratories (see 5.6.2.1.2). 

5.6.3 Reference standards and reference materials 

5.6.3.1 Reference standards 

The laboratory shall have a program and procedure for the calibration of its reference standards. 

Reference standards shall be calibrated by a body that can provide traceability as described in 

5.6.2.1. Such reference standards of measurement held by the laboratory shall be used for 

calibration only and for no other purpose, unless it can be shown that their performance as reference 

standards would not be invalidated. Reference standards shall be calibrated before and after any 

adjustment. 

5.6.3.2 Reference materials

Reference materials shall, where possible, be traceable to SI units of measurement, or to certified 

reference materials. Internal reference materials shall be checked as far as is technically and 

economically practicable. 

5.6.3.3 Intermediate checks 

Checks needed to maintain confidence in the calibration status of reference, primary, transfer or 

working standards and reference materials shall be carried out according to defined procedures and 

schedules 

5.6.3.4 Transport and storage 

The laboratory shall have procedures for safe handling, transport, storage and use of reference 

standards and reference materials in order to prevent contamination or deterioration and in order to 

protect their integrity. 

NOTE Additional procedures may be necessary when reference standards and reference 

materials are used outside the permanent laboratory for tests, calibrations or sampling. 

WMD NOTE Copies of calibration reports for primary standards used in the laboratory are 

maintained in the NIST/WMD. The laboratory must submit updated calibration reports as available. 

If reports are not from NIST, they should be from a NIST-Recognized laboratory or a laboratory 

with formal accreditation from a recognized accreditation body. 
NIST Handbook 143 42 March 2003

5.7 Sampling 

5.7.1 The laboratory shall have a sampling plan and procedures for sampling when it carries out 

sampling of substances, materials or products for subsequent testing or calibration. The sampling 

plan as well as the sampling procedure shall be available at the location where sampling is 

undertaken. Sampling plans shall, whenever reasonable, be based on appropriate statistical methods. 

The sampling process shall address the factors to be controlled to ensure the validity of the test and 

calibration results. 

NOTE 1 Sampling is a defined procedure whereby a part of a substance, material or product is 

taken to provide for testing or calibration of a representative sample of the whole. Sampling may 

also be required by the appropriate specification for which the substance, material or product is to be 

tested or calibrated. In certain cases (e.g., forensic analysis), the sample may not be representative 

but is determined by availability. 

NOTE 2 Sampling procedures should describe the selection, sampling plan, withdrawal and 

preparation of a sample or samples from a substance, material or product to yield the required 

information. 

5.7.2 Where the client requires deviations, additions or exclusions from the documented sampling 

procedure, these shall be recorded in detail with the appropriate sampling data and shall be included 

in all documents containing test and/or calibration results, and shall be communicated to the 

appropriate personnel. 

5.7.3 The laboratory shall have procedures for recording relevant data and operations relating to 

sampling that forms part of the testing or calibration that is undertaken. These records shall include 

the sampling procedure used, the identification of the sampler, environmental conditions (if relevant) 

and diagrams or other equivalent means to identify the sampling location as necessary and, if 

appropriate, the statistics the sampling procedures are based upon. 

5.8 Handling of Test and Calibration Items 

5.8.1 The laboratory shall have procedures for the transportation, receipt, handling, protection, 

storage, retention and/or disposal of test and/or calibration items, including all provisions necessary 

to protect the integrity of the test or calibration item, and to protect the interests of the laboratory and 

the client. 

5.8.2 The laboratory shall have a system for identifying test and/or calibration items. The 

identification shall be retained throughout the life of the item in the laboratory. The system shall be 

designed and operated so as to ensure that items cannot be confused physically or when referred to 

in records or other documents. The system shall, if appropriate, accommodate a subdivision of 

groups of items and the transfer of items within and from the laboratory. 
NIST Handbook 143 43 March 2003

5.8.3 Upon receipt of the test or calibration item, abnormalities or departures from normal or 

specified conditions, as described in the test or calibration method, shall be recorded. When there is 

doubt as to the suitability of an item for test or calibration, or when an item does not conform to the 

description provided, or the test or calibration required is not specified in sufficient detail, the 

laboratory shall consult the client for further instructions before proceeding and shall record the 

discussion. 

5.8.4 The laboratory shall have procedures and appropriate facilities for avoiding deterioration, 

loss or damage to the test or calibration item during storage, handling and preparation. Handling 

instructions provided with the item shall be followed. When items have to be stored or conditioned 

under specified environmental conditions, these conditions shall be maintained, monitored and 

recorded. Where a test or calibration item or a portion of an item is to be held secure, the laboratory 

shall have arrangements for storage and security that protect the condition and integrity of the 

secured items or portions concerned. 

NOTE 1 Where test items are to be returned into service after testing, special care is required 

to ensure that they are not damaged or injured during the handling, testing or storing/waiting 

processes. 

NOTE 2 A sampling procedure and information on storage and transport of samples, including 

information on sampling factors influencing the test or calibration result, should be provided to those 

responsible for taking and transporting the samples. 

NOTE 3 Keeping a test or calibration item secure can be for reasons of record, safety or value, 

or to enable complementary tests and/or calibrations to be performed later. 

5.9 Assuring the Quality of Test and Calibration Results 

The laboratory shall have quality control procedures for monitoring the validity of tests and 

calibrations undertaken. The resulting data shall be recorded in such a way that trends are detectable 

and, where practicable, statistical techniques shall be applied to the reviewing of results. This 

monitoring shall be planned and reviewed and may include, but need not be limited to, the 

following: 

a) regular use of certified reference materials and/or internal quality control using secondary 

reference materials; 

b) participation in interlaboratory comparison or proficiency-testing programs; 

c) replicate tests or calibrations using the same or different methods; 

d) retesting or recalibration of retained items; and 

e) correlation of results for different characteristics of an item. 

NOTE The selected methods should be appropriate for the type and volume of the work 

undertaken. 
NIST Handbook 143 44 March 2003

WMD NOTE The laboratory shall maintain a list of control charts, surveillance activities, and 

round robins maintained or participated in by the laboratory. Measurement control requirements 

must be in place for each measurement service provided by the laboratory. The quality manual 

template contains forms that may be used by the laboratory to list control charts, surveillance 

activities, and proficiency tests. This documentation must be available during on-site assessments 

and submitted to the NIST/WMD as requested. 

5.10 Reporting the Results 

5.10.1 General 

The results of each test, calibration, or series of tests or calibrations carried out by the laboratory 

shall be reported accurately, clearly, unambiguously and objectively, and in accordance with any 

specific instructions in the test or calibration methods. 

The results shall be reported, usually in a test report or a calibration certificate (see note 1), and shall 

include all the information requested by the client and necessary for the interpretation of the test or 

calibration results and all information required by the method used. This information is normally 

that required by 5.10.2, and 5.10.3 or 5.10.4. 

In the case of tests or calibrations performed for internal clients, or in the case of a written agreement 

with the client, the results may be reported in a simplified way. Any information listed in 5.10.2 to 

5.10.4 which is not reported to the client shall be readily available in the laboratory which carried 

out the tests and/or calibrations. 

NOTE 1 Test reports and calibration certificates are sometimes called test certificates and 

calibration reports, respectively. 

NOTE 2 The test reports or calibration certificates may be issued as hard copy or by electronic 

data transfer provided that the requirements of this Handbook are met. 

5.10.2 Test reports and calibration certificates 

Each test report or calibration certificate shall include at least the following information, unless the 

laboratory has valid reasons for not doing so: 

a) a title (e.g., "Test Report" or "Calibration Certificate"); 

b) the name and address of the laboratory, and the location where the tests and/or calibrations were 

carried out, if different from the address of the laboratory; 

c) unique identification of the test report or calibration certificate (such as the serial number), and 

on each page an identification in order to ensure that the page is recognized as a part of the test 

report or calibration certificate, and a clear identification of the end of the test report or 

calibration certificate; 

d) the name and address of the client; 

e) identification of the method used; 
NIST Handbook 143 45 March 2003

f) a description of, the condition of, and unambiguous identification of the item(s) tested or 

calibrated; 

g) the date of receipt of the test or calibration item(s) where this is critical to the validity and 

application of the results, and the date(s) of performance of the test or calibration; 

h) reference to the sampling plan and procedures used by the laboratory or other bodies where 

these are relevant to the validity or application of the results; 

i) the test or calibration results with, where appropriate, the units of measurement; 

j) the name(s), function(s) and signature(s) or equivalent identification of person(s) authorizing 

the test report or calibration certificate; and 

k) where relevant, a statement to the effect that the results relate only to the items tested or 

calibrated. 

WMD NOTE WMD defines the person(s) who authorizes the test report or calibration certificate as 

the Approved Signatory. 

NOTE 1 Hard copies of test reports and calibration certificates should also include the page 

number and total number of pages. 

NOTE 2 It is recommended that laboratories include a statement specifying that the test report 

or calibration certificate shall not be reproduced except in full, without written approval of the 

laboratory. 

5.10.3 Test reports 

5.10.3.1 In addition to the requirements listed in 5.10.2, test reports shall, where necessary for 

the interpretation of the test results, include the following: 

a) deviations from, additions to, or exclusions from the test method, and information on specific 

test conditions, such as environmental conditions; 

b) where relevant, a statement of compliance/non-compliance with requirements and/or 

specifications; 

c) where applicable, a statement on the estimated uncertainty of measurement; information on 

uncertainty is needed in test reports when it is relevant to the validity or application of the test 

results, when a client's instruction so requires, or when the uncertainty affects compliance to a 

specification limit; 

d) where appropriate and needed, opinions and interpretations (see 5.10.5); and 

e) additional information which may be required by specific methods, clients or groups of clients. 

5.10.3.2 In addition to the requirements listed in 5.10.2 and 5.10.3.1, test reports containing 

the results of sampling shall include the following, where necessary for the interpretation of test 

results: 

a) the date of sampling; 

b) unambiguous identification of the substance, material or product sampled (including the name 

of the manufacturer, the model or type of designation and serial numbers as appropriate); 
NIST Handbook 143 46 March 2003

c) the location of sampling, including any diagrams, sketches or photographs; 

d) a reference to the sampling plan and procedures used; 

e) details of any environmental conditions during sampling that may affect the interpretation of the 

test results; and 

f) any standard or other specification for the sampling method or procedure, and deviations, 

additions to or exclusions from the specification concerned. 

5.10.4 Calibration certificates 

5.10.4.1 In addition to the requirements listed in 5.10.2, calibration certificates shall include 

the following, where necessary for the interpretation of calibration results: 

a) the conditions (e.g., environmental) under which the calibrations were made that have an 

influence on the measurement results; 

b) the uncertainty of measurement and/or a statement of compliance with an identified 

metrological specification or clauses thereof; and 

c) evidence that the measurements are traceable (see note 2 in 5.6.2.1.1). 

5.10.4.2 The calibration certificate shall relate only to quantities and the results of functional 

tests. If a statement of compliance with a specification is made, this shall identify which clauses of 

the specification are met or not met. 

When a statement of compliance with a specification is made omitting the measurement results and 

associated uncertainties, the laboratory shall record those results and maintain them for possible 

future reference. 

When statements of compliance are made, the uncertainty of measurement shall be taken into 

account. 

5.10.4.3 When an instrument for calibration has been adjusted or repaired, the calibration 

results before and after adjustment or repair, if available, shall be reported. 

5.10.4.4 A calibration certificate (or calibration label) shall not contain any recommendation 

on the calibration interval except where this has been agreed with the client. This requirement may 

be superseded by legal regulations. 

5.10.5 Opinions and interpretations 

When opinions and interpretations are included, the laboratory shall document the basis upon which 

the opinions and interpretations have been made. Opinions and interpretations shall be clearly 

marked as such in a test report. 

NOTE 1 Opinions and interpretations should not be confused with inspections and product 

certifications as intended in ISO/IEC 17020 and ISO/IEC Guide 65. 
NIST Handbook 143 47 March 2003

NOTE 2 Opinions and interpretations included in a test report may comprise, but not be 

limited to, the following: 

— an opinion on the statement of compliance/noncompliance of the results with requirements; 

— fulfillment of contractual requirements; 

— recommendations on how to use the results; and 

— guidance to be used for improvements.

NOTE 3 In many cases it might be appropriate to communicate the opinions and 

interpretations by direct dialogue with the client. Such dialogue should be written down. 

5.10.6 Testing and calibration results obtained from subcontractors 

When the test report contains results of tests performed by subcontractors, these results shall be 

clearly identified. The subcontractor shall report the results in writing or electronically. 

When a calibration has been subcontracted, the laboratory performing the work shall issue the 

calibration certificate to the contracting laboratory. 

5.10.7 Electronic transmission of results 

In the case of transmission of test or calibration results by telephone, telex, facsimile or other 

electronic or electromagnetic means, the requirements of this Handbook shall be met (see also 

5.4.7). 

5.10.8 Format of reports and certificates 

The format shall be designed to accommodate each type of test or calibration carried out and to 

minimize the possibility of misunderstanding or misuse. 

NOTE 1 Attention should be given to the layout of the test report or calibration certificate, 

especially with regard to the presentation of the test or calibration data and ease of assimilation by 

the reader. 

NOTE 2 The headings should be standardized as far as possible. 

5.10.9 Amendments to test reports and calibration certificates 

Material amendments to a test report or calibration certificate after issue shall be made only in the 

form of a further document, or data transfer, which includes the statement: 

"Supplement to Test Report [or Calibration Certificate], serial number ... [or as otherwise 

identified]," 

or an equivalent form of wording. 
NIST Handbook 143 48 March 2003

Such amendments shall meet all the requirements of this Handbook. 

When it is necessary to issue a complete new test report or calibration certificate, this shall be 

uniquely identified and shall contain a reference to the original that it replaces. 

Table 2. Training requirements

NOTE: The Quality Manual Template (NISTIR 5802) contains a form that can be used to document 

training and dates. 

Recognition Level Training Required For Whom How Often 

· Basic Laboratory 

Metrology Seminar (2 weeks) 

· Basic LAP problems - 

acceptable completion 

Usually all staff, 

at least one staff 

member 

Once 

Once 

Minimum (for legal 

metrological 

activities) 

· Attendance at Regional 

Measurement Assurance Program 

meeting annually 

At least one staff 

member 

Annually 

Calibration 

· All of the above, plus: 

· Intermediate Laboratory 

Metrology Seminar (1 week) 

· Intermediate LAP 

problems - acceptable completion 

Usually all staff; 

at least one 

Every 3 to 4 

years unless 

attending 

RMAP 

annually 

Advanced mass 

calibration 

· All of the above, plus: 

· Advanced Mass 

Measurements Seminar 

· Advanced LAP problems 

completed 

At least one if 

working at this 

level 

At least once; 

for updates as 

needed 

Thermometry 

· Attendance at a NIST 

Precision Thermometry Seminar 

At least one as 

needed 

At least once; 

for updates as 

needed 
NIST Handbook 143 49 March 2003

6. Specific Technical Guidelines

The material in this section is primarily from the Calibration Laboratories Draft Technical Guide 

(1994), and is modified and used here as the technical guidelines for evaluation of traceability 

resulting in the issuance of a Certificate of Measurement Traceability. The following quote, taken 

from the NVLAP Guide is should be considered in its application. 

"This section provides examples and guidelines, not requirements, to technical 

experts and interested calibration laboratories, on good laboratory practices and 

recommended standards. Therefore, the guide language reflects this philosophy 

through the use of "shoulds" instead of "shalls" (along with other less prescriptive 

language) when describing criteria. Absolute requirements are not presented here 

since they depend on the measurement uncertainty for which an applicant laboratory 

wishes to be accredited. This is a business decision for each laboratory and beyond 

the scope of this voluntary program. Simply stated, to be [Recognized or] accredited 

an applicant laboratory must have a quality system and be able to prove (and 

document) that it does what it says it does (i.e., correctly calibrate to a stated 

uncertainty). 

This guide is dynamic in that new parameters may be added and existing criteria 

updated and improved." 

WMD NOTE: Deviation from these recommended criteria must have a technical basis, data, and 

technical analysis to support the variances. 
NIST Handbook 143 50 March 2003

 Recognition Parameter Summary 

Each laboratory must specify the range and uncertainty level for each parameter for which it requests 

Recognition. Uncertainties must be defined at each level. For example, a chart must be available 

that will state each nominal mass, each nominal volume, and so on, with the associated uncertainty. 

Table 3. Recognition parameter summary 

Parameter Range/Application Expanded Uncertainty

Mass laboratory to detail nominal ranges and uncertainties: e.g., 30 kg to 1 mg; Echelon II 

Echelon I ASTM Class 0, 1, OIML Class E1, E2 0.25 mg at 1 kg, and 1 to 5 mg/kg 

Echelon II ASTM Class 2, 3, OIML Class F1, F2 1 mg/kg to 20 mg/kg 

Echelon III ASTM Class 4, 5, 6, 7, OIML Class M1, M2, M3

NIST Class F, legal/regulatory enforcement 20 mg/kg to 1 000 mg/kg 

Length laboratory to specify range: e.g., 10 cm to 20 meter tapes 

Tapes, bench method up to 25 m (100 ft) 0.0 001 m to 0.000 14 m 

Tapes, tape method up to 25 m (100 ft) 0.000 15 m to 0.000 25 m 

Rules, direct comparison up to 0.5 cm (18 in) < 0.000 05 m 

Volume laboratory to specify ranges: e.g., 2 μL micropipettes to 2000 mL glass flasks 

Gravimetric syringes, micropipettes, glass standards, and metal 

provers 

0.000 10 mL/L 

Volume transfer glass standards and metal provers < 0.001 mL/L 

Temperature laboratory to specify type and ranges: e.g., -10 °C to 200 °C; Echelon II 

Echelon I SPRT's ≤ ± 0.005 °C 

Echelon II Thermistors, thermocouples > ± 0.005 °C to ≤ ± 0.05 °C 

Echelon III Liquid-in-glass thermometers > ± 0.05 °C to ≤ ± 0.20 °C 

Echelon IV Liquid-in-glass, dial type, pyrometers > ± 0.20 °C to ≤ ± 1.0 °C 

Echelon V Infrared sensors, thermographs > ± 1.0 °C to ≤ ± 5.0 °C 

Tuning Forks as used for law enforcement 0.05 mph, estimate based on 

interlaboratory tests 

Hydrometers sugar, syrup, petroleum Estimate 

Time stopwatches used for law enforcement significantly less than tolerances; 

estimated at 2 s for a 24 hr test 

Grain Moisture programs for testing grain and commodity moisture 

Oven Methods 0.2 % moisture content 

Chemical Methods 

laboratory to specify methods and products 

0.2 % moisture content
NIST Handbook 143 51 March 2003

6.1 Technical Criteria for Dimensional Laboratories3

6.1.1 Scope

The purpose of this section is to identify the specific technical criteria needed to meaningfully assess 

the competence of a calibration laboratory that performs dimensional calibrations. The artifact 

calibrations currently included in the Recognition program are: 

a) steel tapes; and 

b) rigid rules. 

NOTE: Much of this section applies to dimensional measurements that are more complex than the 

calibration of tapes and rules; however, it is the responsibility of the laboratory to determine which 

sections are applicable. 

6.1.2 References

[1] ANSI/ASME B 89.6.2, Temperature and Humidity Environment for Dimensional 

Measurements (1973, Reaffirmed 2003). 

6.1.3 Statistical Process Control

6.1.3.1 All sources of variability for the calibration should be monitored by subsystem calibration 

(e.g., thermometer, force gage calibration) and the use of check standards to ensure that the 

calibrations are carried out under controlled conditions. The laboratory should maintain and 

document some form of statistical process control (SPC) commensurate with the uncertainty levels 

of the calibration. The SPC control parameters should be based on measurements of check standards 

(or closure parameters resulting from self-calibration or ratio methods) and the repeatability of 

multiple measurements. The frequency and number of process control checks should be appropriate 

for the number of calibrations as well as the level of uncertainty and reliability claimed for the 

calibration. 

6.1.3.2 The laboratory should have control artifacts that adequately span the range of materials and 

sizes normally calibrated by the laboratory. Every measured value of each control should be 

recorded and compared to its historical value to determine that the process is in control. The 

comparison may be made via a plotted control chart with appropriate control limits or by numerical 

comparison using the t-distribution. The expected control values should be updated at least yearly 

using the most current 1 or more years of data. 

 

3 This section is adapted from the NVLAP Calibration Laboratories Draft Technical Guide and is modified for 

WMD application. 
NIST Handbook 143 52 March 2003

6.1.4 Accommodation and Environment

6.1.4.1 The temperature in the calibration area should nominally be 20 °C (degrees Celsius) with a 

maximum variation and rate of change depending on the materials and the uncertainty level needed 

for the calibration. Measurements at temperatures other than 20 °C may be made if the proper 

thermal expansion corrections are applied and the component of uncertainty reflecting the 

uncertainty in thermal expansion coefficients of the artifacts is calculated and added to the total 

uncertainty of the calibration. For comparison measurements the uncertainty component should 

reflect the uncertainty in the thermal expansion of both the master and unknown artifacts. 

6.1.4.2 For length calibrations of the type in legal metrology laboratories, the immediate 

environment should be 20 °C ± 2 °C, and should be measured with an accuracy of 0.5 °C. The 

temperature variation should be less than ± 1 °C over 24 h and ± 0.5 °C during any 1-h period. 

Other environmental conditions may be acceptable as long as the effects are included in the 

uncertainty determination. 

6.1.4.3 The measured length should be corrected to a reference temperature of 20 °C using the 

known linear thermal expansion coefficient of the material. 

6.1.4.4 The temperature stability of the environment should be sufficient for the gage and 

measurement system to be in thermal equilibrium. Measurements may be made in slowly changing 

environments if a suitable measurement model, that includes the effects of the drift, is used. 

Theoretical and experimental verification of the model should be available. 

6.1.4.5 For typical gages made of well characterized materials (steel, carbide or ceramic), 

0.000 001 per °C should be used as the thermal expansion coefficient uncertainty unless there is 

documentation of a lower value. 

6.1.4.6 The relative humidity in the calibration area should not exceed 50 percent. 

6.1.4.7 Excessive vibration should be avoided in the calibration room. If an obvious source of 

vibration exists, precautions should be taken to prevent adverse effects on the laboratory's 

measurements. 

6.1.4.8 The laboratory should have a documented policy regarding responses to problems with the 

environment. 

6.1.5 Equipment and Reference Materials

6.1.5.1 The laboratory should have the equipment needed to make auxiliary measurements on 

artifacts. (e.g., flatness of gage blocks, roundness of ring gages) 

6.1.5.2 The laboratory should have temperature measuring capabilities suitable to the calibration 

procedure. Calibrations involving direct comparisons of artifacts of similar size and materials will, 
NIST Handbook 143 53 March 2003

in general, have modest requirements. Absolute calibrations or comparisons between artifacts of 

different sizes and/or materials will require more accurate temperature measurement. 

6.1.5.3 A laboratory that certifies artifacts to tolerance grades should demonstrate a measurement 

uncertainty which does not exceed 25 % of the tolerance (unless otherwise stated in normative 

standards). Exceptions to this ratio should be accepted for measurement systems that are 

documented to be the state-of-the-art and approved by the customer. 

6.1.5.4 A laboratory that makes mechanical comparisons of masters and test pieces of dissimilar 

materials should have force measuring equipment to determine the force on the probe or probes. A 

correction for differential probe penetration should be applied as long as the probe has maintained its 

rounded shape. On old comparators the probe radius may be altered to the point where a correction 

would induce error. 

6.1.5.5 A laboratory that makes absolute measurements using displacement measuring sensors, such 

as interferometers or linear scales, should have environmental monitoring equipment appropriate to 

the sensor. 

6.1.5.6 A laboratory that makes absolute measurements using a contact device should have force 

measuring equipment to determine the force on the probe or probes. A correction for probe 

penetration should be applied if appropriate. 

6.1.5.7 A laboratory that makes interferometric measurements should have: (1) equipment for 

making high-accuracy temperature measurements, and (2) equipment for determining the index of 

refraction of air. 

6.1.6 Calibration Methods

6.1.6.1 When calibrations are made by comparison to master gages of the different nominal sizes 

the temperature control of the gages and the measurement environment should be improved. 

6.1.6.2 The laboratory should have a manual outlining the procedures to be followed for each type 

of calibration. For calibration of graded sets, the procedure should name the grades that are 

calibrated by the procedure. 

6.1.6.3 The procedures used for related services, such as checks of roundness, relapping, repair, or 

replacement of damaged or out-of-tolerance gages should be clearly stated. 

6.1.6.4 Procedures related to the calibration of rigid rules and tapes used by legal metrology 

laboratories are as follows from NIST Handbook 145: 

a) Bench method for tapes. (SOP 11); 

b) Tape to tape method for tapes. (SOP 12); 

c) Rigid rule calibration. (SOP 10); and 
NIST Handbook 143 54 March 2003

d) Pi tape calibration (SOP 23 - draft). 

6.1.7 Handling of Calibration Items

6.1.7.1 Artifacts should be cleaned and stored in a manner to prevent accidental contact with 

material which could damage the gaging surfaces. 

6.1.7.2 Care should be taken to prevent steel artifacts from rusting. Steel artifacts should be coated 

with a rust inhibiting grease whenever there is a potential for exposure to an environment over 50 % 

relative humidity. If artifacts cannot be greased other materials (e.g., rust inhibiting paper) or 

methods should be used to inhibit rust. 

6.1.7.3 After cleaning, artifacts should be allowed to come to adequate thermal equilibrium in the 

calibration environment before measurement. Artifacts should be placed on a soaking plate or in 

position on the measuring machine long enough to ensure that they are at the proper temperature. 

The soaking time will depend on the size and the thermal properties of the artifacts and plate. 

Specific guidelines for soaking times should be stated in the measurement procedure. The heating 

effects from optical radiation, body heat, and system location should be minimized. 

6.1.7.4 In general, to prevent thermal changes and corrosion of the gaging surfaces, artifacts should 

not be handled with bare hands. Gloves or tongs should be used whenever possible. 

6.1.8 Certificates and Reports

6.1.8.1 All certificates or reports of calibration should contain an uncertainty statement which is 

scientifically determined from measurement data and which agrees with the laboratory's stated 

definition. 

6.1.8.2 The uncertainty should be derived from a model of the measurement system that includes (as 

applicable) the uncertainties caused by: 

a) master artifact calibration; 

b) long term reproducibility of measurement system; 

c) thermal expansion correction for gages and measurement scales; 

a. thermometer calibration, 

b. thermal expansion coefficient, 

c. thermal gradients (internal, gage-gage, gage-scale), 

d) interferometry; 

a. measurement uncertainty of refractometer, 

b. index of refraction formula, 

c. environmental measurements (air temperature, air pressure, humidity, etc.), 

d. calibration of light source frequency, 

e. phase correction for reflected light, 

f. obliquity and slit corrections 

e) instrument geometry; 
NIST Handbook 143 55 March 2003

a. abbe offset and instrument geometry errors, 

b. scale and gage alignment (cosine errors), 

c. gage support geometry (anvil flatness, block flatness), 

f) probe penetration correction; 

g) rotary axis errors (radial and axial displacements, tilt); 

h) analysis algorithms (data fitting, filtering); and 

i) other factors as appropriate. 

6.1.8.3 The method used to affix the calibration items should be described in detail. In general, 

differences in fixture configurations between calibration and use will introduce errors in the 

calibration. 
NIST Handbook 143 56 March 2003

6.2 Technical Criteria for Mass Laboratories4 

6.2.1 Scope

The purpose of this section is to specify the specific technical criteria needed to meaningfully assess 

the competence of a calibration laboratory that performs mass calibrations. 

6.2.1.1 A laboratory should declare its measurement capability in terms of uncertainties for each 

mass value. For many laboratories these uncertainties correspond to three arbitrary echelons of 

measurements that roughly correspond to weight classifications at nominal mass value ranges of 

measurements. For laboratories seeking Recognition at an uncertainty range that corresponds to a 

specific echelon, the scope of Recognition should follow the echelons as defined in Table 4 with a 

declared range of nominal mass values and their associated uncertainties. Recommended ranges of 

mass values are provided in Table 5. A summary of sections 6.2.3, 6.2.5.1, 6.2.5.6, and 6.2.6.1 are 

provided in Table 8. 

6.2.1.2 The echelon stated by the laboratory is associated with the standards, procedures, 

measurement control, facilities, equipment, staff capability, and the overall level of performance 

according to Table 4, and is specifically defined by the expanded uncertainty. Echelons are 

evaluated by all of these factors in addition to the laboratory’s reported uncertainties. 

Table 4. Mass calibration echelons 

Echelon Verification Levels Expanded Uncertainty of the 

Measurements 

 I, (Extra Fine Accuracy) 

 OIML Classes E1, E2

 ASTM Classes 0, 1 

 II, (Fine Accuracy) 

 

 OIML Classes F1, F2

 ASTM Classes 2, 3 

 III, (Medium Accuracy) OIML Classes M1, M2, M3

 ASTM Classes 4, 5, 6, 7 

 NIST Class F 

The expanded uncertainty 

must be less than 1/3 of 

stated tolerances at all levels. 

 

4 This section was originally developed by WMD for adoption in the NVLAP Calibration Laboratories Draft 

Technical Guide; it is modified here for WMD application. 
NIST Handbook 143 57 March 2003

Table 5. Typical "Ranges of Recognition" for mass calibration 

 Echelon Ranges of Recognition 

Nominal Value Ranges 

≥ 30 kg (define limit) 

30 kg to 1 mg 

1 kg to 1 mg I 

100 g to 1 mg 

≥ 30 kg (define limit) for special applications: 

30 kg to 1 mg ≥ 1000 lb (define limit) 

1 kg to 1 mg ≥ 50 lb (define limit) II 

100 g to 1 mg 50 lb to 0.001 lb 

≥ 30 kg (define limit) normal applications: 

30 kg to 1 g ≥ 1000 lb (define limit) 

1 kg to 1 g ≥ 50 lb (define limit) III 

100 g to 1 g 50 lb to 0.001 lb 

6.2.1.3 The reported uncertainty of mass standards calibrated by a mass calibration laboratory will 

vary depending on available balances, the uncertainty of reference standards, and the nominal value 

of the mass standard being tested. Thus, a laboratory may perform calibrations at Echelon I in some 

ranges, for example at 1 kg, and may perform calibrations at Echelon II, e.g., 20 kg, in other ranges. 

The laboratory performs calibrations in a specified range as requested; however, all laboratories may 

not be capable of meeting the requirements of all echelons. Differing equipment, skills, knowledge, 

measurement control, and demonstrated competence are required for each of the echelons. 

Demonstrated competence in one echelon is not sufficient to guarantee adequate performance in the 

others. 

6.2.2 References

[1] ANSI/ASTM E 617, Standard Specification for Laboratory Weights and Precision Mass 

Standards, 1997. 

[2] OIML R 111, Weights of Classes E1, E2, F1, F2, M1, M2, M3, 1994 (under revision in 2003). 

[3] NIST Handbook 105-1, Specifications and tolerances for Reference Standards and field 

Standard Weights and Measures, Specifications and Tolerances for Field Standard Weights, 

(NIST Class F), 1990. 
NIST Handbook 143 58 March 2003

[4] NBS Technical Note 844, Designs for the Calibration of Small Groups of Standards in the 

Presence of Drift, Cameron, J. M., Hailes, G. E., 1974. 

[5] NBS Technical Note 952, Designs for the Calibration of Standards of Mass, Cameron, J. M., 

Croarkin, M. C., Raybold, R. C., 1977. 

[6] NISTIR 5672, Advanced Mass Calibrations and Measurement Assurance Program 

Requirements for State Calibration Laboratories, Fraley, K. L., Harris, G. L., 1995. 

 

[7] NISTIR 6969, Selected Laboratory and Measurement Practices, and Procedures, to Support 

Basic Mass Calibrations, Harris, G. L., Torres, J. A., 2003. 

6.2.3 Statistical Process Control

6.2.3.1 Appropriate measurement assurance programs should be in place and available for review 

for each echelon and nominal mass range for which calibration data is provided. Note Table 8 for 

appropriate measurement control programs for each echelon. Appropriate data includes balance 

standard deviations that represent process variation and well-characterized check standard values. 

6.2.3.2 Measurement assurance techniques should exhibit results consistent with the procedures 

used to perform calibrations and should be integral to the measurement to accurately reflect the 

measurement process. For those situations where statistical information is not inherent to the 

process, i.e., simple measurements without built-in redundancy checks, additional measurements 

should be made to provide experimental characterization of the measurement sufficient for an 

adequate estimation of the process uncertainty. Those data should be available for review. 

6.2.4 Accommodation and Environment

6.2.4.1 To be deemed capable of making adequate measurements, calibration laboratories should 

provide an environment with adequate environmental controls appropriate for the level of 

measurements to be made, according to echelons defined herein. The environmental conditions are 

summarized in Table 6. 
NIST Handbook 143 59 March 2003

Table 6. Environmental facility guidelines for mass laboratories

Echelon Temperature Relative Humidity 

(maximum per 4 hours) 

I 20 °C to 23 °C, a set point ± 1 °C 

maximum change 0.5 °C/h 40 % to 60 % ± 5 % 

II 20 °C to 23 °C, a set point ± 2 °C 

maximum change 1.0 °C/h 40 % to 60 % ± 10 % 

III 

18 °C to 27 °C 

maximum change 2 °C/h 

40 % to 60 % ± 20 % 

NOTE: The environmental conditions should also be within the specifications of the weighing 

instruments where applicable. 

6.2.4.2 Cleanliness guidelines are usually met without clean-room type air handling systems by 

maintaining clean-room type practices. Excessive air exchange rates negatively affect balance 

performance. The laboratory should maintain limited access to the calibration area and minimize 

contamination (provide a clean surface) for locations where calibration items are being tested. 

Activities such as smoking, eating, or drinking and items such as paper products, printers, and files 

contribute to the difficulty of maintaining adequate cleanliness and are not recommended. A 

positive pressure, laminar-type air flow is usually needed to maintain cleanliness recommendations 

and to minimize air currents. 

6.2.4.3 Vibration should not diminish the performance of precision analytical balances and mass 

comparators. Proximity to heavy machinery, railways, heavily traveled highways, or similar sources 

of known vibration is not recommended. Steps are often taken to attenuate vibration to an 

acceptable level of stability with methods such as massive piers (solid marble or concrete tables), 

isolated foundations, or elimination of the source. Balances and mass comparators used for 

Echelons I and II generally require massive piers, independent piers, and/or an isolated foundation; 

pneumatic or hydraulic tables are inappropriate. 

6.2.4.4 Undesirable effects due to static electricity should be controlled, if needed, with methods 

such as humidity, antistatic deionizing radiation devices, the grounding of balances or operators, or 

with the use of special conductive flooring and selection of proper clothing for staff. 

6.2.5 Equipment and Reference Materials

6.2.5.1 Minimum reference standards should be available at each echelon and range, for which the 

laboratory is Recognized, as recommended in Table 8. Sufficient historical data and uncertainty 

analysis should be available to support the standards used. 

6.2.5.2 The accuracy of auxiliary instruments for Echelons I and II, (e.g., scale, analytical balance, 

mass comparator) is less important than the precision of the instrument due to algorithms used in 

mass calibration. However if such equipment is repaired, it should be reevaluated to ascertain its 
NIST Handbook 143 60 March 2003

current level of precision prior to use, and the uncertainty estimate should reflect the post repair 

performance. 

6.2.5.3 The precision of the scale, analytical balance, or mass comparator, as determined through 

appropriate process control charts, should be suitable for the echelon at which it is used. For an 

application where external standards are used for comparison, appropriate control charts should be 

maintained to evaluate the process standard deviation. Note Table 8 summary for further evaluation. 

6.2.5.4 Means should be provided to measure barometric air pressure, air temperature, and relative 

humidity of the laboratory environment as indicated in Table 7; documentation of the accuracy and 

traceability is required. These instruments should be used in close proximity to the balance being 

used. For Echelon I, temperature may be measured inside the weighing chamber when there is a 

difference between the air temperature in the balance chamber and the surrounding area. For 

Echelon III, where buoyancy corrections are generally negligible, recording environmental data is 

useful in the support of general environmental requirements of the previous section but the accuracy 

generally does not affect measurement results. 

Table 7. Environmental equipment accuracy (expanded uncertainty) 

Parameter Barometric Pressure Temperature Relative 

Humidity 

 Echelon I ± 65 Pa (0.5 mm Hg) ± 0.1 °C ± 5 % 

 Echelon II ± 135 Pa (1.0 mm Hg) ± 0.5 °C ± 10 % 

 Echelon III The laboratory maintains documented accuracy. 

6.2.5.5 For Echelon I, the laboratory should state the presence of a possible systematic error in the 

combined uncertainty associated with the use of an assumed density in the primary or reference 

standards (additional Type B component) or the laboratory should have appropriate means to 

measure the density of mass standards. If the magnetic susceptibility of the mass standards is 

evaluated, it should be indicated on calibration reports. The methods used to determine density or 

magnetic susceptibility should be documented. 

6.2.5.6 Each mass standard used as a reference standard by the laboratory should be calibrated by 

NIST or by an accredited or Recognized laboratory with capability adequate to sustain the accuracy 

required and maintain traceability to BIPM. The laboratory should provide evidence, such as 

periodic surveillance, that the standard is, in principle, acceptable for providing calibration services 

at each echelon. Note Table 8 for traceability guidelines. 

6.2.5.7 Balances used as a direct comparison to the mass unit, should be given a verification test or 

calibration prior to use. For an application requiring balance accuracy, the laboratory should choose 

appropriate and correct calibration algorithms. Balances used as dividers and multipliers of the mass 

unit should be capable of the appropriate accuracy and linearity requirements of the accuracy class 

for which they are used. Calibration of built-in standards should be performed periodically and 
NIST Handbook 143 61 March 2003

should be verified prior to use. History from measurement control programs (surveillance testing) 

may be used to determine calibration intervals. 

6.2.5.8 Instruments used to monitor environmental conditions in the laboratory should be traceable 

to a suitable national laboratory (directly or via an accredited or Recognized laboratory) and be 

recalibrated periodically unless defining standards are employed. Calibration periods will be 

documented by the laboratory. 

6.2.6 Calibration Methods

6.2.6.1 The algorithm chosen for the measurement, the reference standard to be used, and the 

equipment to be used for a particular calibration should provide acceptable levels of uncertainty for 

that calibration. A documented procedure should be available in the laboratory to determine the 

correct algorithm. Note Table 8 for guidelines. 

6.2.6.2 Computer programs should have passed software quality analysis. Computer programs 

should be tested, using standard data sets designed to magnify errors, as an effective way of showing 

that program errors are not present which do not affect some measurements but cause others to be 

incorrect. Computer programs should be documented in detail. The documentation should include 

technical references that provide the basis for the algorithm, the weighing equation, and the data set 

used to test the program for errors. 

6.2.7 Handling of Calibration Items

6.2.7.1 The laboratory should have documented procedures to ensure adequate chain-of-custody of 

calibration items if required by law. 

6.2.7.2 The laboratory will document appropriate procedures to ensure that cleaning, if performed, 

ensures the integrity of the standards, and to provide for thermal conditioning, where appropriate. 

6.2.7.3 The laboratory must allow adequate stabilization time for mass standards to ensure 

environmental and thermal stability prior to calibration. 

6.2.7.4 Documented procedures to ensure adequate tracking of calibration items should be 

appropriate to the class of mass standard. Strings, tags, or labels fastened to the standard are 

inappropriate. 

6.2.8 Certificates and Reports

6.2.8.1 Certificates and reports should describe the mass standards mentioned in the report with 

sufficient detail to avoid any ambiguity. For Echelons I and II, additional items to be included on a 

test report, are: mass (true mass) values, conventional (apparent) mass values, reference density, 

uncertainties, material, thermal coefficient of expansion (if used in calculations), construction, 

density (measured or assumed), and any identifying markings. 
NIST Handbook 143 62 March 2003

6.2.8.2 Environmental parameters measured during the test should be provided on certificates and 

reports for Echelons I and II. Typical ranges are acceptable for reporting conditions for Echelon III. 

These include laboratory temperature, barometric pressure and relative humidity. 

6.2.8.3 Information regarding cleaning methods (if requested) should be provided on the test report. 

6.2.8.4 Reports may include reference to OIML or ASTM classification schemes and tolerances. 

Calibration items being tested should meet appropriate specifications for evaluation as well as 

tolerances. It is the responsibility of the requestor of the calibration to select classifications 

acceptable for their needs. In the case where magnetism, surface finish, and density are not tested 

for Echelon I and II, a statement to that effect should be included on the calibration report. 

6.2.8.5 The weight surface of a mass standard should be free of any sign of abuse or damage. Signs 

of abuse or misuse include the placement of labels, tags, wires or other material on mass standards. 

In addition, visible dirt and fingerprints are a sign of misuse for Echelons I and II. It is 

recommended that the calibration laboratory establish appropriate means for notifying customers 

regarding any unusual factors such as signs of abuse regarding the mass standard being tested should 

be included on the report. Out of tolerance conditions should be reported when significant or when 

requested.
NIST Handbook 143 63 March 2003

Table 8. Summary of technical criteria for mass calibration

Echelon Minimum Measurement Control Minimum Reference Standards Minimum Traceability 

I (Extra Fine) 

• Process control charts • Check standards for each decade, with long term 

standard deviation 

• Surveillance of all standards • Proficiency Testing 

-on-site assessment -round robin participation 

• OIML Class E1, or E2 or 

• ASTM Class 0, 1 

• single piece, highly polished 

• NIST, or other national level 

calibration every 2 to 5 years based on measurement process data and independent verification, or 

• NIST Mass MAP, or 

• User operated mass calibration 

package, on-site to verify traceability (when available). 

II (Fine) 

• Process control charts 

• Check standards for each decade, with long term 

standard deviation 

• Surveillance of selected standards Proficiency 

Testing 

 -on-site assessment  -round robin participation 

• OIML Class E1, or E2

• ASTM Class 0, 1; or • single piece, highly polished 

• NIST calibration every 2 to 5 

years based on measurement process data and independent verification, or 

• Calibration by accredited or 

Recognized Echelon I laboratory, if uncertainty requirements can be met. 

III (Medium) 

• Process control charts 

• Check standards for each balance Proficiency 

Testing 

 -on-site assessment  -round robin participation 

• Working standards such as: • ASTM Class 2, 3 

Or 

• OIML Class F1

• two piece acceptable, fine 

finish 

• Calibration of all working 

standards by NIST every 2 to 5 years based on measurement process data and independent verification, or 

• Calibration of all working 

standards by an Echelon I or II accredited or Recognized labs every 2 to 5 years based on measurement process data and independent verification 
NIST Handbook 143 64 March 2003

6.3 Technical Criteria for Volume Laboratories5 

6.3.1 Scope

The purpose of this section is to specify the specific technical criteria needed to meaningfully assess 

the competence of a calibration laboratory that performs volume calibrations. It should be noted that 

the procedures affect the achievable uncertainty. 

Table 9. Typical “Ranges of Recognition” for volumetric calibration

Procedure 

Types Scope of Recognition - Nominal Value Range 

Glassware 

Standard Pipets & Syringes 

Metal Test Measures or Provers 

≥ 1 L ≥ 2 000 L or ≥ 500 gal 

1 L to 100 mL 100 L < V < 2 000 L or 25 < V < 500 gal 

Gravimetric 

100 mL to 1 μL 100 mL to 1 μL ≤ 100 L or ≤ 25 gal 

Glassware Metal Test Measures or Provers 

≥ 1 L or 1 qt ≥ 2 000 L or ≥ 500 gal 

100 mL < V < 1 L or 1 gill < V < 1 qt 100 L < V < 2 000 L or 25 < V < 500 gal 

Volume 

Transfer 

 ··· ≤ 100 L or ≤ 25 gal 

6.3.1.1 Volumetric units are derived from mass units. Volume calibrations may be determined by 

either a gravimetric (weighing procedure) or a volume transfer (comparative) method. The two 

methods require different technical requirements and both are defined here. The measurement of 

volume by metering methods (and meter calibration) is outside the scope of this document. 

6.3.1.2 The gravimetric procedure is based on the conservation of mass principle where a 

determination of the mass of water contained in or delivered from the vessel that is being calibrated 

is used to define volume. The mass values are determined in air, are corrected for air buoyancy 

effects, and are corrected to appropriate reference temperatures. The accuracy and precision will 

vary depending on balances used, the purity of the water, the ability to make accurate temperature 

measurements, the nominal value of the volume standard being tested, and the ability to make 

adequate mass measurements. 

 

5 This section was originally developed by WMD for adoption in the NVLAP Calibration Laboratories Draft 

Technical Guide; it is modified here for WMD application.
NIST Handbook 143 65 March 2003

6.3.1.3 In the volume transfer procedure, water is delivered from a primary volume standard to the 

vessel under test. Temperature corrections are made to compensate for the cubical coefficients of 

thermal expansion of the standard, test vessel, and water to a specified reference temperature. The 

accuracy and precision will vary considerably depending on the presence of a meniscus, the 

cleanliness and drain characteristics of the container, the cleanliness and purity of the water, and the 

ability to make adequate temperature measurements. 

6.3.2 References

[1] ANSI/ASTM E 287-02, Standard Specification for Laboratory Glass Graduated Burets 

(2002). 

[2] ANSI/ASTM E 288-94 (1988), Standard Specification for Laboratory Glass Volumetric 

Flasks. 

[3] ANSI/ASTM E 438-92 (2001) e1, Standard Specification for Glasses in Laboratory 

Apparatus. 

[4] ANSI/ASTM E 542-01, Standard Practice for Calibration of Volumetric Apparatus. 

[5] ANSI/ASTM E 694-99, Standard Specification for Laboratory Glass Volumetric Apparatus. 

[6] ANSI/ASTM E 969-02, Standard Specification for Glass Volumetric (Transfer) Pipets. 

[7] OIML R 4 (1972), Volumetric Flasks (one mark) in Glass. 

[8] OIML R 40 (1981), Graduated Pipettes for Verification Officers. 

[9] OIML R 41 (1977), Standard Burettes for Verification Officers. 

[10] OIML R 43 (1977), Standard Graduated Glass Flasks for Verification Officers. 

[11] NIST Handbook 105-2, 105-3, 105-4 Specifications and Tolerances for Reference Standards 

and Field Standard Weights and Measures; Specifications and Tolerances for Field Standard 

Glass Flasks, Open-neck Provers, and LPG Volumetric Provers. 

[12] API Manual of Petroleum Measurement Standards, Chapter 4 - Proving Systems; Section 3, 

Small Volume Provers, 1988; Section 4, Tank Provers, 1988; Section 7, Field Standard Test 

Measures, 1998. 
NIST Handbook 143 66 March 2003

6.3.3 Statistical Process Control

6.3.3.1 Appropriate measurement control programs should be in place and available for review for 

each measurement type (based on procedures) and nominal volume range for which calibration data 

is provided. Note Table 12 for appropriate measurement control programs for each measurement 

type. Appropriate data includes standard deviations and range values that represent process 

variation and well characterized check standard values. 

6.3.3.2 Measurement control techniques should exhibit results consistent with the procedures used 

to perform calibrations and should be integrated into the measurement to accurately reflect the 

measurement process. For those situations where statistical information is not inherent to the 

process, i.e., simple measurements without built-in redundancy checks, additional measurements 

should be made to provide experimental characterization of the measurement sufficient for an 

adequate estimation of the process uncertainty. Those data should be available for review. 

6.3.4 Accommodation and Environment

6.3.4.1 To be deemed capable of making adequate measurements, calibration laboratories should 

provide a facility with adequate environmental controls appropriate for the level of measurements to 

be made, according to procedure types as shown in Table 10. Lower relative humidity may increase 

measurement error due to evaporation. 

Table 10. Environmental facility guidelines for volumetric calibration

Procedure Temperature Relative Humidity 

(maximum range per 4 hours) 

I 

Gravimetric 

20 °C to 23 °C, set point ± 2 °C 

maximum change 1.0 °C/h 40 % to 60 % ± 10 % 

II 

Volume Transfer 

18 °C to 27 °C 

maximum change 2.0 °C/h 

40 % to 60 % ± 20 % 

NOTE: The environmental conditions should also be within the specifications of applicable 

equipment. 

6.3.4.2 The environment in which testing activities are undertaken should not invalidate the results 

or adversely affect the required accuracy. Particular care should be taken when such calibration 

practices are undertaken at sites other than the permanent laboratory facility to minimize the effects 

of uncontrolled environments. 

6.3.4.3 Vibration, air currents, rapid temperature fluctuations, and other environmental concerns 

should not diminish the accuracy and precision of volume transfer methods or the performance of 

precision balances or scales when gravimetric methods are used. 
NIST Handbook 143 67 March 2003

6.3.4.4 The quality of water used as a calibration medium should be of adequate purity (potable) 

and cleanliness, and should be free from excess air entrapment. For gravimetric procedures the 

density should be calculated/measured to the nearest 0.00001 g/cm3

. 

6.3.5 Equipment and reference materials

6.3.5.1 Mass standards used as reference standards should be traceable to a national laboratory 

(such as NIST) and be available at each class and range, for which the laboratory is Recognized, as 

recommended in Table 12. Sufficient historical data and uncertainty analysis should be available to 

support the standards used. 

6.3.5.2 Volume standards used as reference standards in the laboratory should be traceable to a 

national laboratory (such as NIST) and the laboratory should have appropriate procedures in place 

for verification and recalibration. The accuracy of the primary volume standards of the laboratory 

should be appropriate for the accuracy class of services provided. 

6.3.5.3 Gravimetric methods, which generally use water as calibration media, require the 

verification of an adequate supply of deionized or distilled water. 

6.3.5.4 Gravimetric methods require the use of weighing equipment with adequate accuracy and 

precision for the uncertainty of the measurement procedure. Appropriate control charts or range 

charts should be maintained to verify the measurement process. 

6.3.5.5 Gravimetric methods require the means to adequately measure barometric air pressure, air 

temperature, water temperature, and relative humidity of the laboratory environment. Volumetric 

methods require temperature measurements. Environmental measuring equipment should be 

available with the accuracy indicated in Table 11. Relative humidity may need to be monitored 

more closely if evaporation is a concern. 

Table 11. Environmental equipment accuracy (expanded uncertainty) 

 Procedure Type 

 

 Barometric 

 Pressure 

 Temperature 

 water/air 

 Relative Humidity 

 Gravimetric ± 135 Pa 

(1.0 mm Hg) 

 ± 0.1 °C / ± 0.5 °C ± 10 % 

 Volume Transfer Not essential ± 0.5 °C Not essential 

6.3.6 Calibration methods

6.3.6.1 The algorithm chosen for the measurement, the reference standard to be used, and the 

equipment to be used for a particular calibration should be correct for that calibration. A 
NIST Handbook 143 68 March 2003

documented procedure should be available in the laboratory to determine the correct algorithm. 

(Examples are provided in NIST Handbook 145 Standard Operating Procedures, SOPs.) 

6.3.6.2 Computer programs should have passed software quality analysis. Computer programs 

should be documented in detail. The documentation should include technical references that 

provided the basis for the algorithm, any weighing equations, and data set used to test the program 

for errors. 

6.3.7 Handling of calibration items

6.3.7.1 The laboratory should have documented procedures to ensure adequate chain-of-custody of 

calibration items if required by law. 

6.3.7.2 Appropriate procedures should be documented to ensure adequate tracking of calibration 

items that are appropriate for glass or metal volumetric standards. 

6.3.8 Certificates and reports

6.3.8.1 Calibration reports should describe the volume standards mentioned in the report with 

sufficient detail to avoid any ambiguity. Additional items to be included on a test report are: 

volume, uncertainty, reference temperature, material, thermal coefficient of expansion (assumed or 

measured), construction, any identifying markings, and any tolerances if appropriate. 

6.3.8.2 Environmental parameters measured during the test should be provided on the test report as 

appropriate. These include laboratory temperature, volume standard temperature, barometric 

pressure and relative humidity. 

6.3.8.3 Volume standards being tested should meet the appropriate specifications such as NIST, 

ASTM, API, or OIML, if required by laboratory customers. It is the responsibility of laboratory 

customers to determine acceptable accuracy levels for their needs. 

6.3.8.4 The calibration item (volume standard) should be free of any sign of abuse or damage. 

Signs of abuse or misuse include dents, chips, improper draining due to lack of cleanliness, and dirty 

sight gages. Out of tolerance conditions should be reported. 
NIST Handbook 143 69 March 2003

Table 12. Summary of technical criteria for volumetric calibration

Procedure 

Minimum 

Measurement 

Control 

Minimum 

Reference 

Standard 

Minimum 

Traceability 

I 

Gravimetric 

• Process control charts • Check standards • Surveillance of all 

standards used to provide measurement services 

• Proficiency testing - On-site assessment - Round robin participation 

• Appropriate mass 

standards 

- ASTM Class 2 or 3; or 

- OIML Class F1 or F2; 

or - Calibrated Balance 

• NIST, or national level 

calibration periodically, based on independent historical data verification 

or • - Test of weighing equipment 

using correct methods of calibration and adjustment with traceable mass standards 

• Docum

calibr

or • NIST 

substi

or • - Use 

II 

Volume 

Transfer 

• Process control charts • Check standards • Surveillance of selected 

standards 

• Proficiency testing - On-site assessment - Round robin participation 

Primary volume standards with accuracy and repeatability characteristics acceptable for the type of service provided 

• Original NIST calibration and 

periodic independent verification 

or • Calibration by accredited or 

Recognized laboratory, if uncertainty requirements can be met 

Documentwater drawby NIST, 
NIST Handbook 143 70 March 2003

6.4 Technical Criteria for Hydrometer Laboratories6 

6.4.1 Scope

This section outlines the specific technical requirements in accordance with which a laboratory 

should demonstrate that it operates if it is to be Recognized as competent to carry out calibrations of 

hydrometers. 

6.4.2 References

[1] ASTM E 100-95 (2001): Standard Specification for ASTM Hydrometers. 

[2] ASTM E 126-92 (1998): Standard Method for Inspection and Verification of Hydrometers. 

6.4.3 Statistical process control

6.4.3.1 All sources of variability for the hydrometer calibration should be monitored. Check 

standards should be used to ensure that the calibrations are carried out under controlled conditions. 

The laboratory should maintain statistical process control (SPC) commensurate with the accuracy 

levels needed for the calibration. The SPC control parameters should be based on measurements of 

check standards (or closure parameters) and the repeatability of multiple measurements. The 

frequency and number of process control checks should be appropriate for the level of uncertainty 

claimed for the calibration. 

6.4.3.2 The laboratory should have control hydrometers that adequately span the range of materials 

and sizes normally calibrated by the laboratory. Every measured value of each control should be 

recorded and compared to its historic value to determine whether or not the process is in control. 

These values should be plotted on a control chart that has upper and lower control limits. 

6.4.4 Accommodation and environment

6.4.4.1 The environmental conditions (i.e., temperature, atmospheric pressure and relative humidity) 

in the hydrometer calibration area should have no more than the maximum variations permitted, 

depending on the materials and the accuracy level needed for the calibration. The reference 

temperature for a particular hydrometer scale may vary from 15.56 °C (15.56 °C is approximately 

60 °F, which is the reference temperature for petroleum products in the United States) to 20 °C. The 

laboratory should have the appropriate instrumentation required to measure the environmental 

conditions. 

6.4.4.2 The density of the water used in hydrometer calibrations should be known to within 

0.000005 g/cm3

. Specific gravity is expressed as the ratio of the density of a liquid to the density of 

water at a specified temperature. 

 

6 This section is adapted from the NVLAP Calibration Laboratories Draft Technical Guide, and modified for WMD 

application. 
NIST Handbook 143 71 March 2003

6.4.4.3 Vibration of equipment used in the hydrometer calibrations should be reduced to noninfluential levels. If an obvious source of vibration exists, it should not adversely affect the 

laboratory's claimed uncertainty level. 

6.4.4.4 Any laboratory that makes hydrometer comparisons should have an appropriate supply of 

calibration fluids with suitable surface tensions. Hydrometers should be calibrated in the liquids in 

which they are to be used. 

6.4.4.5 Calibration liquids should be stored in an approved safety cabinet. Laboratories that make 

hydrometer comparisons should abide by all safety requirements set forth by a regulatory counsel, 

(e.g., chemical labeling, EPA and OSHA guidelines, etc.). 

6.4.5 Equipment and reference materials

6.4.5.1 The laboratory should have the appropriate equipment required to perform hydrometer 

calibrations at the Recognized level. All equipment should be properly maintained. 

6.4.5.2 The laboratory that performs hydrometer comparisons should have master hydrometers for 

which the calibrations are directly traceable to the appropriate national standards laboratory. The 

appropriate calibration corrections to these master hydrometers should be applied. 

6.4.5.3 The laboratory should have the equipment needed to make auxiliary measurements of 

hydrometers, (e.g., balances, mass standards, knowledge of water density, etc.). 

6.4.5.4 Any laboratory that makes hydrometer comparisons should abide by all safety requirements 

set forth by a regulatory counsel, (e.g., chemical labeling, EPA and OSHA guidelines, etc.). 

6.4.5.5 The laboratory should have temperature measuring capabilities suitable to the calibration 

procedure. In the case of measuring the specific gravity of a liquid with a master hydrometer, 

temperature measurement of the liquid accurate to ± 0.01 °C is required. 

6.4.5.6 A laboratory that makes hydrometer comparisons should have a ventilated chemical hood to 

exhaust any harmful fumes from the working area. 

6.4.6 Calibration methods 

6.4.6.1 The wide use of hydrometers for many different purposes has led to various stem scales for 

unique applications (e.g., specific gravity, percentage alcohol, degrees API, degrees Baume and 

Brix). The appropriate stem scale should be evaluated. 

 

6.4.6.2 Ideally, hydrometers under test are compared directly to master hydrometers in the kinds of 

liquids in which they are to be used. This comparison is performed in a clear, smooth glass cylinder 
NIST Handbook 143 72 March 2003

of suitable size. The calibration liquid should be well stirred before each comparison to minimize 

temperature gradient in the liquid. 

6.4.6.3 The laboratory should have a manual detailing the procedures to follow for each type of 

hydrometers being calibrated. This manual should contain all pertinent information needed for 

calibration at a given Recognition level. 

6.4.7 Handling of calibration items

6.4.7.1 Hydrometers should be cleaned and stored in a manner that prevents accidental contact with 

material that could damage the calibration surfaces. Since hydrometers are made of glass and can be 

easily broken, they should be handled only by an experienced operator. 

6.4.7.2 Inspection should be made of all hydrometers for calibration for bent stems, twisted scales, 

and loose material inside the body of the hydrometer. 

6.4.7.3 The hydrometer should be wiped with alcohol and dried to ensure a clean surface before it is 

immersed in the calibration liquid. 

6.4.8 Certificates and reports

6.4.8.1 Summary sheets and data sheets should be used to document all calibrations. This 

documentation should be dated and initialed by the operator. A historical registry should be kept. 

6.4.8.2 The uncertainty reported for the hydrometer should be derived from a model of the 

measurement system that includes, as applicable, the uncertainties due to: 

a) master hydrometer; 

b) long term reproducibility of measurement system; 

c) thermal expansion; and 

d) other appropriate factors. 
NIST Handbook 143 73 March 2003

6.5 Technical Criteria for Thermometer Laboratories7 

6.5.1 Scope

6.5.1.1 This section contains the specific technical criteria in accordance with which a laboratory 

should demonstrate that it operates, if it is to be Recognized as competent to carry out thermometer 

calibrations. 

6.5.1.2. This section may also be used as a guide by thermometer calibration laboratories in the 

development and implementation of their quality systems. 

Echelon: Level of performance associated with the level of total uncertainty, according to the 

following table: 

Echelon Expanded Uncertainty 

I ≤ ± 0.005 °C 

II > ± 0.005 °C to ≤ ± 0.05 °C 

III > ± 0.05 °C to ≤ ± 0.20 °C 

IV > ± 0.20 °C to ≤ ± 1.0 °C 

V > ± 1.0 °C to ≤ ± 5.0 °C 

NOTE: The uncertainty of thermometers calibrated by the laboratory will vary depending upon the 

temperature range of application, even for the same thermometer. Thus, a laboratory may perform 

calibrations at Echelon II in some cases and Echelon III or IV in other cases because of the 

temperature ranges involved. Also, the echelon assigned is dependent on the types of thermometers 

calibrated. 

6.5.2 References

[1] ASTM Annual Book of Standards, Volume 14.03, Standards Relating to Temperature 

Measurement (latest edition). 

[2] NIST Handbook 105-6, Specifications and Tolerances for Field Standard Thermometers 

(1997). 

[3] NIST SP 250-23, Liquid-In-Glass Thermometer Calibration Service (1988). 

 

7 This section is adapted from the NVLAP Calibration Laboratories Draft Technical Guide, and modified for WMD 

application. 
NIST Handbook 143 74 March 2003

[4] NBS Monograph 174, Thermometer Calibration, A Model for State Calibration 

Laboratories (Appendix A: NBS Monograph 150, Liquid-In-Glass Thermometry) (1985). 

6.5.3 Statistical process control 

6.5.3.1 Fixed-point cell and triple point of water as the reference standards

When the reference standard used by the laboratory is a fixed-point cell, the three action items 

described below are required as indicated by the application table that follows their description. 

6.5.3.1.1 Records of complete phase equilibrium plateaus obtained for each cell upon receipt and 

every 6 months thereafter should be maintained. This should include either manually recorded 

temperatures at consistent intervals, or a graphical representation of the equilibrium plateau, as 

measured by the monitoring sensor. 

6.5.3.1.2 A separate check thermometer should be used for each cell and control charts maintained. 

6.5.3.1.3 The triple point of water should be measured after every measurement at another 

temperature. 

Echelon 

Item 

I II III IV V 

6.5.3.1.1 X X X X 

6.5.3.1.2 X X X X 

6.5.3.1.3 X 

6.5.3.2 SPRT or RIRT as the reference standard

When the reference standard used by the laboratory is a standard platinum resistance thermometer 

(SPRT) or a rhodium-iron resistance thermometer (RIRT), the two action items described below are 

recommended as indicated by the application table that follows them. 

6.5.3.2.1 There should be documentation (i.e., control charts) to show that the resistance of the 

instrument at the triple point of water has not changed since its last calibration by more than the 

equivalent shown in the table below. 

6.5.3.2.2 If a digital voltmeter (DVM), digital multi-meter (DMM), or digital temperature indicator 

is used, the calibration of the temperature indicating system (indicator and sensor) should be 

checked periodically at either the water triple point or at the ice point. 
NIST Handbook 143 75 March 2003

Item Echelon 

I II III IV V 

6.5.3.2.1 2 mK 2 mK 5 mK 10 mK 10 mK 

6.5.3.2.2 X X X X 

6.5.3.3 Thermistor thermometer as the reference standard

When the reference standard used by the laboratory is a thermistor thermometer, the two action 

items described below are recommended as indicated by the application table that follows them. 

6.5.3.3.1 The calibration of the thermistor thermometer should be checked frequently (monthly or 

weekly) depending on the particular application, and control charts should be kept. 

6.5.3.3.2 If, since the last calibration, the resistance of the thermistor thermometer has changed at a 

reference check point (fixed-point, preferably) by the equivalent shown in the next table, a new 

calibration should be done. 

Item Echelon 

I II III IV V 

6.5.3.3.1 x x x x 

6.5.3.3.2 2 mK 5 mK 10 mK 

6.5.3.4 Thermocouple as the reference standard

When the reference standard used by the laboratory is a thermocouple, control charts should show 

the reproducibility at appropriate fixed points. 

6.5.3.4.1 Liquid-in-glass thermometer as the reference standard

When the reference standard used by the laboratory is a liquid-in-glass thermometer, the two action 

items described below are recommended as indicated by the application table that follows them. 

6.5.3.4.1.1 The total-immersion mercury-in-glass thermometer should be checked according to good 

laboratory practice. One method is to check at the ice point on a daily basis after use and maintain 

records. 
NIST Handbook 143 76 March 2003

6.5.3.4.1.2 The total-immersion liquid-in-glass thermometer should be checked according to good 

laboratory practice. One method is to check at the ice point weekly and maintain control charts. 

Item Echelon 

I II III IV V 

6.5.3.4.1.1 X X 

6.5.3.4.1.2 X 

6.5.4 Accommodation and environment

6.5.4.1 For all echelons, the environmental conditions of the laboratory should be controlled. 

6.5.4.2 The temperature of the laboratory should be controlled to ± 2 °C. 

6.5.4.3 The relative humidity should be controlled between 40 % and 60 %. 

6.5.4.4 Vibrations in the laboratory should be minimized. 

6.5.5 Equipment and reference materials

6.5.5.1 Reference standards

The following table indicates which reference standard is acceptable for each echelon. 

Acceptable reference standard Echelon 

I II III IV V 

Fixed-point cell X X X X 

SPRT and/or RIRT X X X X X 

Thermistor thermometer X X X X 

Gold/platinum thermocouple X X X X 

Type S, R or B thermocouple X X X 

Total-immersion liquid-in-glass X X X 
NIST Handbook 143 77 March 2003

6.5.5.2 Fixed-point cell as the reference standard

6.5.5.2.1 The purity of the fixed-point material should be at least 99.999 9 % and the other starting 

materials of construction of the cells should be of ultra-high purity also. If the cells are unsealed, 

they should be filled at all times with an inert gas such as argon. 

6.5.5.2.2 The cells should be of the defining fixed points of the ITS-90, or well-characterized, stable 

and reproducible secondary fixed points. 

6.5.5.3 SPRT or RIRT as the reference standard

6.5.5.3.1 A system having adequate resolution and uncertainty should be used to measure a 

reference SPRT or RIRT. Recommendations for specific situations are given below. 

6.5.5.3.2 A resistance bridge having at least the resolution shown below, as a function of claimed 

total uncertainty, is recommended. A ratio bridge and standard resistors may also be used: 

Echelon Claimed expanded 

uncertainty 

Minimum 

bridge resolution 

I ≤ ± 0.01 °C 10 μΩ

II ± 0.05 °C 50 μΩ

III near ± 0.20 °C 200 μΩ

IV near ± 1.0 °C 1 mΩ

6.5.5.3.3 Alternatively, a DVM or DMM with the resolution shown below, and a constant-current 

source with provision for reversing the current, may be used. The current should be known to the 

same accuracy as the DVM or DMM. 

Echelon DVM or DMM resolution 

(digits) 

I 6.5 

II 6.5 

III 6.5 

IV 6.5 
NIST Handbook 143 78 March 2003

6.5.5.4 Thermocouple as the reference standard

If the reference standard is a noble metal thermocouple used with a scanner, a scanner with 

low-thermal switches should be used. 

6.5.6 Measurement traceability and calibration

6.5.6.1 Fixed-point cell as the reference standard

When the reference standard is a fixed-point cell, the four action items described below are 

recommended as indicated by the application table that follows them. 

6.5.6.1.1 The cell should be evaluated by NIST; or 

6.5.6.1.2 The cell may have been evaluated by the supplier, if the supplier documented in detail the 

preparation and evaluation, showing direct traceability to NIST, or is NVLAP accredited; or 

6.5.6.1.3 The cell should have been evaluated by a NVLAP accredited supplier. 

6.5.6.1.4 The maximum uncertainty of the temperature of the cell should be as indicated in the next 

table: 

Item Echelon 

I II III IV 

6.5.6.1.1 X X*

6.5.6.1.2 X**

6.5.6.1.3 X X 

6.5.6.1.4 ± l mK ≤ ± 0.005 °C 0.01 °C ± 0.02 °C 

*

 for total uncertainties ≤± 0.01 °C ** for total uncertainties in range ± 0.01 °C to ± 0.05 °C 

6.5.6.2 SPRT or RIRT as the reference standard

When the reference standard is an SPRT or RIRT, the four action items described below are 

recommended as indicated by the application table that follows them. 
NIST Handbook 143 79 March 2003

6.5.6.2.1 The SPRT or RIRT should be calibrated by NIST or a NVLAP accredited laboratory 

every 2 years but may be calibrated by NIST every 2 to 5 years if adequate measurement process 

data is evident. 

6.5.6.2.2. The SPRT or RIRT should be calibrated annually, and all reference resistors used with the 

bridge should be calibrated traceable to NIST. 

6.5.6.2.3 If a bridge is used, it should be calibrated annually, and all reference resistors used with 

the bridge should be calibrated traceable to NIST. 

6.5.6.2.4 If a DVM or DMM is used, it should be calibrated annually. 

Item Echelon 

I II III IV V 

6.5.6.2.1 X X X X 

6.5.6.2.2 X 

6.5.6.2.3 X X X X 

6.5.6.2.4 X X X X X 

6.5.6.3 If a thermistor thermometer is the reference standard, it should be calibrated traceable 

to NIST. 

6.5.6.4 If a thermocouple is the reference standard, documentation should show that its 

calibration is traceable to NIST and indicate the annealing procedure used during the thermocouple's 

use. 

6.5.6.5 If a liquid-in-glass thermometer is the reference standard, it should be calibrated 

traceable to NIST. 

6.5.7 Calibration methods

6.5.7.1 All computer programs used in data logging and analysis should be documented in detail. 

Also, all algorithms and equipment should be correct for the task. 

6.5.7.2 When calibrations are performed by comparison against an SPRT or an RIRT, or a 

thermistor thermometer, or a liquid-in-glass thermometer, the five action items described below are 

recommended as indicated by the application table that follows them. 
NIST Handbook 143 80 March 2003

6.5.7.2.1 If a liquid medium is used, it should be stirred vigorously and a comparison block should 

be located in the bath to aid in improving the uniformity. 

6.5.7.2.2 If a liquid medium is used, it should be adequately stirred and a comparison block should 

be located in the bath to aid in improving the uniformity. 

6.5.7.2.3 If the comparison medium is a liquid, it should be adequately stirred. 

6.5.7.2.4 The uniformity of the comparison medium should be measured by means of a fastresponding thermometer. 

6.5.7.2.5 The temperature stability and uniformity of the comparison medium should be as shown in 

the next table. 

Echelon Item 

I II III IV V 

6.5.7.2.1 X X 

6.5.7.2.2 X X 

6.5.7.2.3 X 

6.5.7.2.4 X X 

6.5.7.2.5 ± 0.5 mK ± 0.5 mK* (a) (a) (a) 

*

For claimed expanded uncertainty < ± 0.01 °C. For claimed expanded uncertainty > ± 0.01 °C, at 

least 10 times better than the claimed expanded uncertainty. 

(a) At least 10 times better than the claimed expanded uncertainty. 

6.5.7.3 When the reference standard is a total-immersion mercury-in-glass thermometer, 

corrections obtained from measurements at the ice point should be made for all temperature 

measurements. 

6.5.7.4 The ice-point bath should be made according to accepted procedures from ice made from 

distilled water. This applies to Echelons III, IV and V. 

6.5.8 Handling of calibration items 

In addition to the general requirements set forth for all calibration items, it should be noted that 

SPRT's are susceptible to and need protection from shock and vibration in shipping, handling, and 

storage. 
NIST Handbook 143 81 March 2003

6.6 Technical Criteria for Moisture Laboratories8 - Grain and/or Commodities 

6.6.1 Scope

6.6.1.1 The purpose of this section is to specify the specific technical criteria needed to 

meaningfully assess the competence of a testing laboratory that performs moisture analyses. 

6.6.1.2 This document may also be used as a guide by moisture laboratories in the development 

and implementation of their quality systems. 

6.6.1.3 Laboratories may be Recognized based on procedures used to determine moisture. These 

four procedural categories identify the method of moisture determination and the reference methods. 

The scope of Recognition follows the categories as defined in Table 13. Laboratories may be 

Recognized under two or more categories if they have the necessary equipment, skills, knowledge, 

measurement control and demonstrated competence to perform adequately in each category. 

NOTE: The national laboratory for grain moisture in the United States is the Grain Inspection 

Packers and Stockyards Administration (GIPSA) formerly known as the Federal Grain Inspection 

Service (FGIS). The standard method recognized by the GIPSA laboratory is the Air Oven Method. 

Grain moisture testing laboratories should reference the Air Oven Method and participate in 

interlaboratory comparisons to ensure comparability of measurements with the national laboratory. 

Table 13. Moisture determination laboratory classifications

Procedural 

Category Moisture Determination Method Reference Methods

Ia Air Oven 

GIPSA, Technical Services Division, Air 

Oven Moisture Reference Laboratory 

Working Instructions 

I 

Oven Methods 

Ib Vacuum Oven 

AOAC Official Methods of Analysis, 17th 

ed. Revision 1, 2002, vacuum oven 

methods, Sec. 32 

IIa Karl Fischer chemical 

analysis 

AOAC Official Methods of Analysis, 17th 

ed. Revision 1, 2002, Karl Fischer methods 

AOAC, Automatic Karl Fischer Titration of 

Moisture in Grain, (Vol. 64, No. 6, 1981) II 

Chemical Method 

IIb Basic Reference Method ISO 711, Cereals and Cereal ProductsDetermination of Moisture Content 

 

8 This section was originally developed by WMD. 
NIST Handbook 143 82 March 2003

6.6.1.4 Laboratories should document the grains and/or commodities tested and maintain replicate 

results within ± 0.2 %. The scope of Recognition should indicate identified grains and/or 

commodities and the uncertainty limits. Uncertainty analysis should be completed according to the 

ISO Guide for the Expression of Uncertainty in Measurement. 

6.6.1.5 Important definitions in this section follow: 

Moisture content - The loss in mass, expressed as a percentage, undergone by the product under the 

conditions specified in this document. 

Air Oven - A device that uses gravity convection or mechanical convection (forced-draft) to heat air 

in a chamber to its controlled temperature. 

Vacuum Oven - A device that uses a vacuum to alter the pressure within the oven chamber and 

maintain a temperature at that specific pressure. 

Karl Fischer Titration - A procedure that involves the simultaneous grinding of grain/commodity 

and extraction of the water with methanol and the subsequent titration of the extract with Karl Fisher 

reagent. 

Basic Reference Method - An ISO procedure (ISO Guide 711) using oven and chemicals to 

determine moisture content of a product. 

6.6.2 References

[1] United States Department of Agriculture, Grain Inspection Packers and Stockyards 

Administration, (GIPSA), Technical Services Division, Air Oven Moisture Reference 

Laboratory Working Instructions, April 1998 (Internal Documents). 

[2] ASTM E 145-68, Standard Specification for Gravity-Convection and Forced-Ventilation 

Ovens (reapproved 1987). 

[3] Association of Official Analytical Chemists (AOAC), Official Methods of Analysis, 17th 

Edition Revision 1, 2002. 

[4] AOAC, Automatic Karl Fischer Titration of Moisture in Grain, Volume 64, No. 6, 1981. 

[5] Anderson, J. E. "Storage of Cereal Grains and Their Products," Chapter 1, Moisture - Its 

Significance, Behavior, and Measurement. (Hunt, W. Haward, Pixton, S. W.). 

[6] ISO 711, International Standard, Cereals and Cereal Products - Determination of 

Moisture Content (Basic Reference Method) Second edition, 1985. 

[7] Scholz, Eugen, Karl Fischer Titration, 1984. 
NIST Handbook 143 83 March 2003

6.6.3 Statistical Process Control 

6.6.3.1 An appropriate statistical process control system should be in place including procedures 

for measurement verification through participation in interlaboratory comparisons between the 

laboratory, GIPSA and other laboratories. 

6.6.3.2 It is critical that testing results remain consistent with previous laboratory test results; 

repeated tests should remain within the laboratories documented uncertainties and be evaluated 

using statistical methods. 

 

6.6.3.3 A laboratory should have an operating procedure to review data for trends and failures to 

indicate where failure has occurred. Records of corrective action, repair, or recalibration should also 

be maintained. 

6.6.4 Accommodation and environment

6.6.4.1 To make adequate measurements, moisture determination laboratories should have a 

facility with adequate environmental controls appropriate for the laboratory classification. 

 

6.6.4.2 Due to the extreme hygroscopic properties of ground grain (oven methods) and methanol 

(Karl Fischer chemical method), humidity and temperature should be controlled within the following 

parameters: 

Temperature: 20 °C to 23 °C, set point ± 2 °C, maximum change of 1.0 °C/h; and 

Humidity: 40 % to 60 % ± 10 % 

NOTE: Sample exposure to the environment should be minimized throughout the collection, 

storage, and testing process. 

6.6.4.3 To prevent contamination of test samples, from grain and/or commodity dust particles, 

adequate cleanliness should be maintained. 

6.6.4.4 Adequate space should be available for sample storage, preparation and testing and be 

appropriately organized for efficient operation. Laboratory equipment should be logically placed to 

accommodate handling of samples, operation and maintenance of equipment and to prevent 

accidental sample substitution. 

6.6.4.5 Grains and/or commodities under test should be kept in refrigerated storage areas. The 

refrigerated storage areas should be maintained between 1.5 °C and 7.0 °C. 

6.6.4.6 Excess vibration may adversely affect the performance of precision analytical balances and 

mass comparators and should be prevented. Proximity to heavy machinery, railways, heavily 

traveled highways, or similar sources of known vibration is not recommended. Steps should be 
NIST Handbook 143 84 March 2003

taken to reduce vibration to an acceptable level of stability with methods such as isolated 

foundations for balances or elimination of the source. 

6.6.4.7 Laboratories should ensure that electrical disturbances that affect moisture results are kept 

at a minimum. 

6.6.4.8 Undesirable effects due to static electricity should be controlled as needed by maintaining 

appropriate laboratory humidity or with antistatic deionizing radiation devices. The grounding of 

balances or operators, or the use of special conductive flooring may also be used. 

6.6.5 Equipment and Reference materials

6.6.5.1 Standard Reference Materials 

6.6.5.1.1 Category Ia and Ib laboratories - The grains and/or commodities are prepared for use as 

reference standards according to documented procedures for oven testing. During preparation, 

storage and distribution, care should be taken to ensure reference sample integrity. 

6.6.5.1.2 Category IIa and IIb laboratories - Specified reagents are used according to manufacturers' 

instructions for the specific type of Karl Fischer titration equipment in use. Category IIb 

laboratories generally should use chemicals specified in International Standard ISO 711, Sec. 7. 

During sample preparation, the integrity of the reagents and samples is critical. 

6.6.5.2 Primary Equipment - Oven methods 

6.6.5.2.1 Category Ia laboratories should have appropriate equipment for the moisture 

determination of grain and/or commodity moisture: mechanical (forced draft) or gravity convection 

ovens, desiccator, mill, moisture dishes, and analytical balance. Reference GIPSA Technical 

Services Division, Air Oven Moisture Reference Laboratory Working Instructions for equipment 

specifications. 

NOTE: The use of a mechanical convection (forced draft) oven is strongly recommended. Tests 

have shown that ovens of the forced-draft type have more uniform temperature due to heat 

circulation, the temperature recovery is more rapid after insertion of samples and will accommodate 

more samples than gravity convection ovens. 

NOTE: Laboratories should have temperature monitoring devices with suitable accuracy and 

traceability to record oven temperatures during moisture testing. 

6.6.5.2.2 Category Ib laboratories should have appropriate equipment for the moisture 

determination of grain and/or commodities: vacuum oven desiccator, mill, moisture dishes, and 

analytical balance with the same requirements as class Ia laboratories. Reference AOAC, Official 

Methods of Test for equipment specifications. 
NIST Handbook 143 85 March 2003

6.6.5.3 Primary Equipment - Karl Fischer chemical analysis 

6.6.5.3.1 Category IIa laboratories should have appropriate equipment for the moisture 

determination of grain and/or commodities: Karl Fischer Titration Assembly (manual or automatic 

with a stirrer), mill, centrifuge, and analytical balance. Reference manufacturers' instructions and 

Karl Fischer Titration, Eugen Scholz, 1984. 

6.6.5.3.2 Category IIb laboratories should have appropriate equipment for the moisture 

determination of grain and/or commodities: analytical balance, apparatus for reducing pressure, mill, 

dishes, cup, drying tube, oven, air-drying train, and desiccator. Reference International Standard 

ISO 711 for equipment specifications. 

6.6.5.4 Secondary Equipment

6.6.5.4.1 Laboratories should measure air temperature and relative humidity of the laboratory 

environment. Instruments are used in close proximity to the grain and/or commodity tested. 

Laboratory ovens should be equipped with calibrated, accurate and traceable thermometers (accurate 

within ± 0.5 °C) to ensure the accuracy of the oven temperature. 

6.6.5.4.2 Samples should be stored in clean, air-tight and moisture-proof glass containers or plastic 

bags to prevent the loss or gain of moisture in the product. Plastic bags should have a thickness of at 

least 0.1 mm (4 mil, 0.004 in). A thickness of 0.15 mm (6 mil, 0.006 in) is preferred due to greater 

durability. 

6.6.6 Measurement traceability and calibration

6.6.6.1 Since direct traceability to a standard (national measurement unit) is not possible for 

moisture measurements of the type described here, and the Federal standard for grain moisture is 

defined by comparison to GIPSA results, it is critical for the laboratory to participate in 

interlaboratory comparison programs to establish "comparability" of the results between the 

laboratories. 

6.6.6.2 It is essential that moisture testing equipment that affects the accuracy of the moisture 

measurement (e.g., to include thermometers and balances) be periodically calibrated or verified for 

accuracy and traceability. 

6.6.6.3 Balances used in determining moisture content should be periodically verified or calibrated 

prior to use. 

6.6.6.4 Instruments used to monitor environmental conditions in the laboratory should be 

periodically recalibrated. Appropriate calibration intervals should be established and documented by 

the laboratory. 

6.6.7 Moisture determination methods
NIST Handbook 143 86 March 2003

6.6.7.1 The types of moisture determination methods employed, and equipment used, should be 

appropriate for the grains and/or commodities being tested based on the procedural category. 

Measurement methods should provide acceptable repeatability. A documented procedure for each 

method should be available. 

6.6.7.2 Computer programs used in the moisture determination of grains and/or commodities 

should have passed software quality analysis. Computer programs may be tested, using standard 

data sets designed to magnify errors, as an effective way of showing that program errors do not 

effect some measurements but cause others to be incorrect. Computer programs should be 

documented in detail. Documentation should include technical references that provide the basis for 

the algorithm, the moisture equations, and the data set used to test the program for errors. 

6.6.8 Handling of grain and/or commodities for moisture determination 

6.6.8.1 The laboratory should have documented procedures to ensure that all samples are properly 

and uniquely marked upon receipt to include: the type of sample and a nonrepetitive identification 

number to ensure adequate tracking of samples in laboratory and field. 

6.6.8.2 The laboratory should document appropriate procedures for proper cleaning and storage of 

samples to ensure integrity. 

6.6.8.3 Documented procedures should be maintained that ensure that subportions of the sample 

under test are representative of the whole. 

NOTE: Care should be taken during sample collection and handling to prevent contamination of the 

sample with body oil or moisture, and to protect the sample from extreme environmental moisture 

and temperature. 

6.6.9 Test Reports

6.6.9.1 Reports when necessary, should include: moisture determination results, sample type, 

condition and identification number, type of moisture determination used to ascertain the results, and 

the precision of measurement (repeatability between the dishes or duplicate runs.) 

6.6.9.2 Environmental parameters measured during the test should be provided on reports. These 

include laboratory temperature and relative humidity. 

6.6.9.3 Information regarding cleaning methods (if performed) should be provided on the test 

report. 
NIST Handbook 143 87 March 2003

Table 14. Summary of environmental facility guidelines (as described in Section 6) 

Lab 

Temperature 

range °C 

(set point) 

± Temp 

variability °C 

Max change 

per hour °C 

Temp 

accuracy °C RH % range 

RH % 

accurac

(change pe

hours) 

Mass I 20 to 23 1.0 0.5 0.1 40 to 60 5 Mass II 20 to 23 2.0 1.0 0.5 40 to 60 10 Mass III 18 to 27 2.0 40 to 60 20 Volume - G 20 to 23 2.0 1.0 0.1/0.5 (H2O, air) 40 to 60 10 Volume - T 18 to 27 1.0 2.0 0.5 40 to 60 Dimensional 20 (18 to 22) 1.0 0.5 > 50 20 Temperature 2.0 40 to 60 10 Tuning Forks Hydrometers 0.01 (bath) Time Grain Moisture 20 to 23 2.0 1.0 0.5 40 to 60 
NIST Handbook 143 88 March 2003

7. References

ANSI/NCSL Z540.1-1994 (R2002), American National Standards Institute, National Conference 

of Standards Laboratories, American National Standard, General Requirements for Calibration 

Laboratories and Measuring and Test Equipment. 

ISO/IEC 10012-1, International Organization for Standardization, International Standard 

10012-1, Quality Assurance Requirements for Measuring Equipment, Part 1, Metrological 

Confirmation System for Measuring Equipment, 1992. 

ISO/IEC Guide 17025, International Organization for Standardization, General Requirements for 

the Competence of Testing and Calibration Laboratories, 1999. 

NCSL Recommended Practice RP-7: Laboratory Design, July 1993. 

NCSL Recommended Practice RP-11: Reports and Certificates of Calibration, October 1991. 

NBS Handbook 145, Handbook for the Quality Assurance of Metrological Measurements, 

Oppermann, H.V., Taylor, J., 1985. 

NIST Handbook 150, National Voluntary Laboratory Accreditation Program, NVLAP, 

Procedures and General Requirements, Alderman, D. F., Faison, C. D., White, V. R., editors, 

July 2001. 
NIST Handbook 143 89 March 2003

8. Glossary 

The following section contains the definitions of a number of terms in the sense in which they are 

used throughout this Handbook. Where applicable, definitions are taken from: 1) NIST Handbook 

150, NVLAP Procedures and General Requirements, 1994, wherever possible; 2) The International 

Vocabulary of Basic and General Terms in Metrology (VIM:1994); or 3) NIST Handbook 143, 

Program Handbook, 1997 edition. Many of the NIST Handbook 150 definitions are taken from the 

VIM:1994. 

Accreditation - a formal Recognition that a laboratory is competent to carry out specific tests or 

calibrations or types of tests or calibrations. (HB 150) 

Accreditation Criteria - a set of requirements used by an accrediting body which a laboratory must 

meet in order to be accredited. (HB 150) 

Accreditation Process - the process of demonstrating whether a calibration laboratory is capable of 

fulfilling specified accreditation requirements. 

Approved Signatory (of an accredited laboratory) - an individual who is Recognized by WMD as 

competent to sign official laboratory calibration or test reports. (HB 150, modified) 

NOTE: The Approved Signatory is responsible for the technical content of the report and is the 

person to be contacted by WMD, laboratory clients, or others in case of questions or problems with 

the report. Approved Signatories shall be persons with responsibility, authority, and technical 

capability within the organization for the results produced. The laboratory must maintain a list of 

Approved Signatories and make that list available for review during on-site assessments and to 

WMD upon request. 

Authorized Representative (of a Recognized laboratory) - an individual who is authorized by the 

laboratory or the parent organization to sign the WMD Request for Recognition form and commit 

the laboratory to fulfill the WMD requirements. (The Authorized Representative may also be 

recommended by the laboratory as an Approved Signatory. Only the Authorized Representative can 

authorize a change in the scope or nature of the laboratory's Request for Recognition.) (HB 150, 

modified) 

Calibration - a set of operations which establish, under specified conditions, the relationship 

between values indicated by a measuring instrument or measuring system, or values represented by a 

material measure, and the corresponding known values of a measurand. (HB 150) 

Also: comparison of a measurement standard or instrument with another standard or instrument to 

detect, correlate, report, or eliminate by adjustment any inaccuracy of the compared. 
NIST Handbook 143 90 March 2003

Certificate of Measurement Traceability - a certificate issued to a weights and measures laboratory 

indicating that the laboratory has traceable standards, can make and provide traceable measurements, 

and complies with the requirements of NIST Handbook 143, Program Handbook. 

Corrective Action - an action taken to eliminate the causes of an existing deficiency or other 

undesirable situation in order to prevent recurrence. 

Deficiency - the non-fulfillment of NIST/WMD conditions and/or criteria for Recognition (or 

accreditation). (HB 150, modified) 

Good Laboratory Practices (GLP) - an acceptable way to perform some basic operation or activity 

in a laboratory, that is known, or believed to influence, the quality of its outputs. GLPs ordinarily 

are essentially independent of the measurement techniques used. (HB 143, 1997) 

Good Measurement Practices (GMP) - an acceptable way to perform some operation associated 

with a specific measurement technique, and which is known or believed to influence the quality of 

the measurement. (HB 143, 1997) 

Interlaboratory Comparisons - organization, performance and evaluation of calibrations or tests on 

the same or similar items or materials by two or more laboratories in accordance with predetermined 

conditions. (HB 150) 

Internal Assessment - the process of self-appraisal of a calibration or testing laboratory using 

specified general and technical criteria and checklists to evaluate compliance to accreditation 

requirements; may be used as a quality management review as well. 

Laboratory - an organization that performs calibrations and/or tests. When a laboratory is part of an 

organization that carries out activities additional to calibration and testing, the term "laboratory" 

refers only to those parts of that organization that are involved in the calibration and testing process. 

The laboratory activities may be carried out at or from a permanent location, at or from a temporary 

facility, or in or from a mobile facility. (HB 150) 

Length Laboratory - a specific area, within a metrology laboratory, that is used solely for calibration 

or tolerance testing of length standards. (HB 143, 1997) 

Mass Laboratory - a specific area, within a metrology laboratory, that is used solely for calibration 

or tolerance testing of mass standards or test weights; generally divided into small mass (≤ 10 kg) 

and large mass (> 10 kg) areas. (HB 143, 1997) 

Measurement Assurance - a process to ensure adequate measurement results that may include, but 

is not limited to: 1) use of good experimental design principles so that the entire measurement 

process, its components, and relevant influence factors can be well characterized, monitored, and 

controlled; 2) complete experimental characterization of the measurement process uncertainty 
NIST Handbook 143 91 March 2003

including statistical variations, contributions from all known or suspected influence factors, 

imported uncertainties, and the propagation of uncertainties throughout the measurement process; 

and 3) continuously monitoring the performance and state of statistical control of the measurement 

process with proven statistical process control techniques including the measurement of wellcharacterized check standards along with the normal workload and the use of appropriate control 

charts. (HB 150) 

NVLAP - the NIST National Voluntary Laboratory Accreditation Program. 

On-Site Assessment - a formal examination or official inspection of a calibration or testing 

laboratory to evaluate its compliance with specific laboratory accreditation criteria. 

OWM - The NIST Office of Weights and Measures (now Weights and Measures Division). 

Proficiency Testing - the determination of laboratory performance by means of comparing and 

evaluating calibrations or tests on the same or similar items or materials by two or more laboratories 

in accordance with predetermined conditions. (HB 150) 

Preventive Action - an action taken to eliminate the cause of a potential deficiency or other 

undesirable situation in order to prevent occurrence. 

Quality Audit - a systematic and independent examination to determine whether quality activities 

and related results comply with planned arrangements and whether these arrangements are 

implemented effectively, and are suitable to achieve objectives. (HB 150) 

Quality Control - the operational techniques and activities that are used to fulfill requirements for 

quality. 

Quality Manual - A document stating the quality policy, quality system, and quality practices of an 

organization. The quality manual may reference other laboratory documentation. (HB 150) 

Recognition - the evaluation and issuance of a Certificate of Measurement Traceability and letter 

regarding the laboratory quality system for weights and measures laboratories (not a formal 

accreditation). 

RMAP - Regional Measurement Assurance Program. A regional approach to ensuring measurement 

assurance through periodic gathering to conduct training, interlaboratory comparisons, and 

continuous improvement activities. WMD jointly operates six regional MAPs in cooperation with 

the State laboratories. 

Scope of Accreditation - A document issued by an accreditation body which lists the test methods or 

services, or calibration services for which the laboratory is accredited. The scope for each 

measurement area includes the range and the best uncertainty reported at each level. (HB 150) 
NIST Handbook 143 92 March 2003

Standard, Check (or control) - a standard that is used as part of a process measurement assurance 

program to provide a "check" on the process and standards to ensure that the standards, measurement 

results, and measurement processes are within acceptable statistical limits. 

Standard, Intrinsic - Intrinsic standards are based on well-characterized laws of physics, 

fundamental constants, or invariant properties of materials, and they make ideal stable, precise, and 

accurate measurement standards if properly designed, characterized, operated, monitored and 

maintained. (NCSL, Traceability Resolution Meeting. 1/25/96) 

Standard, Primary - A standard that is designated or widely acknowledged as having the highest 

metrological qualities and whose value is accepted without reference to other standards of the same 

quantity. (HB 150) 

Standard, Reference - A standard, generally of the highest metrological quality available at a given 

location, from which measurements made at that location are derived. (HB 150) 

Standard, Secondary - a standard whose value is assigned by comparison with a primary standard 

of the same quantity. (HB 150) 

Standard, Working - a standard that is usually calibrated against a reference standard, and is used 

routinely to calibrate or check material measures, measuring instruments, or reference materials. 

(HB 150) 

Standard Operating Procedure (SOP) - a procedure adopted for repetitive use when performing a 

specific measurement or sampling operation. It may be a standard method or one developed by the 

user. (HB 143, 1997) 

State Laboratory Program - A program of the NIST Weights and Measures Division designated to 

provide guidance, technical support, and assistance to State legal metrology laboratories to ensure 

accurate and traceable measurements from NIST to the local jurisdictions. 

Temperature Laboratory - a specific area, within a metrology laboratory, that is used solely for 

calibration or tolerance testing of temperature standards. 

Tolerance Testing - a measurement operation performed to determine whether the actual value of a 

standard, artifact, or instrument is within a permitted tolerance of its nominal value. An error and 

uncertainty value must first be determined before one can assess the tolerance status. (HB 143, 

1997) 

Traceability - the property of the result of a measurement or the value of a standard whereby it can 

be related to stated references, usually national or international standards, through an unbroken chain 

of comparisons all having stated uncertainties. (VIM:1994) 
NIST Handbook 143 93 March 2003

A measurement quality assurance system and periodic verification are required to ensure that the 

accuracy of the measurement is within the stated limits of uncertainty. 

Uncertainty - parameter, associated with the result of a measurement, that characterizes the 

dispersion of the values that could reasonably be attributed to the measurand. (HB 150) 

Volume Laboratory - a specific area, within a metrology laboratory, that is used solely for 

calibration or tolerance testing of volume standards; generally divided into small volume (≤ 20 L) 

and large volume (> 20 L) areas. (HB 143, 1997) 

WMD - The NIST Weights and Measures Division. Formerly NIST Office of Weights and 

Measures (OWM). 
NIST Handbook 143 94 March 2003

 Appendix A. List of Services Available from NIST

It is the objective of NIST to encourage all State laboratories to seek full Recognition and formal 

accreditation. Technical assistance and consultation includes the following: 

1. BASIC metrology training in mass, length, and volume (2-week seminar). 

2. INTERMEDIATE metrology training in mass, length, and volume (1-week seminar). 

Prerequisite - completion of BASIC course and BASIC LAP problems or equivalent. 

3. NIST Precision Measurement Seminars. Seminars on special measurement techniques (2 

to 5 day duration). Examples - Precision Thermometry Seminar, Advanced Mass 

Seminar. 

4. Recommended test procedures for: 

 

a. mass tolerance testing 

b. mass calibration weighing designs 

c. volume calibration 

- volume transfer 

- gravimetric 

d. length calibration 

- length bench 

- tape-to-tape 

- rigid rules 

e. temperature - NBS Monograph 150 

5. Time and frequency information - NBS Special Publications 432 and 559. 

6. Measurement assurance information - NBSIR 77-1240 and regional measurement 

assurance programs. 

7. NIST evaluation of laboratory auditing problems. 

8. NIST evaluation of laboratory facilities by on-site visit. 

9. Measurement control programs in selected measurement areas. 

For further details on any of the above, general information, or assistance in areas not listed above, 

or in the case of special measurement problems, contact: 

Weights and Measures Division, State Laboratory Program 

National Institute of Standards and Technology 

Gaithersburg, MD 20899 

Phone: 301/975-4004 

Fax: 301/926-0647 

http://www.nist.gov/owm 
NIST Handbook 143 95 March 2003

Appendix B. Request for Recognition, Scope of Recognition, Approved 

Signatories, Authorized Representative

Name of laboratory

Address of laboratory

Scope of Recognition - complete Appendix D with uncertainty estimates included 

Approved Signatories - have assigned responsibility for validity of laboratory reports 

Authorized Representative - contact for administration of laboratory Recognition 
NIST Handbook 143 96 March 2003

Appendix C. Laboratory Assessment Checklist 

(from NVLAP Handbook 150, 2001) 

GENERAL OPERATIONS CHECKLIST 

Instructions to the Assessor (or Quality Manager): This checklist addresses the general 

accreditation criteria prescribed in NIST Handbook 150, NVLAP Procedures and General 

Requirements (2001 edition). The checklist items are numbered to correspond to the requirements 

found in Sections 4 and 5 of the Handbook. Items marked with a F were not sufficiently addressed in 

the previous version of this Handbook. 

Place an "X" beside each checklist item that represents a deficiency. Place a "C" beside each item 

on which you are commenting for other reasons. Record the item number and written deficiency 

explanation and/or comment on the comment sheet(s) at the end of the checklist. Write "OK" beside 

all other items you observed or verified as compliant at the laboratory. Identify policies and 

procedures where called for. 

4 Management requirements for accreditation

4.1 Organization 

____ 4.1.1 The laboratory or the organization of which it is part shall be an entity that can be held 

legally responsible. 

 

 Legal name of laboratory ownership: ___________________________________ 

 

____ 4.1.2 It is the responsibility of the laboratory to carry out its testing and calibration activities in 

such a way as to meet the requirements of this Handbook and to satisfy the needs of the 

client, the regulatory authorities or organizations providing recognition. 

 

____ 4.1.3 The laboratory management system shall cover work carried out in the laboratory’s 

permanent facilities, at sites away from its permanent facilities, or in associated temporary or 

mobile facilities. 

 

____ 4.1.4 If the laboratory is part of an organization performing activities other than testing and/or 

calibration, the responsibilities of key personnel in the organization that have an involvement 

or influence on the testing and/or calibration activities of the laboratory shall be defined in 

order to identify potential conflicts of interest. 

NOTE 1 Where a laboratory is part of a larger organization, the organizational arrangements should 

be such that departments having conflicting interests, such as production, commercial marketing or 

financing do not adversely influence the laboratory's compliance with the requirements of this 

Handbook. 

NOTE 2 If the laboratory wishes to be Recognized as a third-party laboratory, it should be able to 

demonstrate that it is impartial and that it and its personnel are free from any undue commercial, 

financial and other pressures which might influence their technical judgment. The third-party testing 

or calibration laboratory should not engage in any activities that may endanger the trust in its 

independence of judgment and integrity in relation to its testing or calibration activities. 

 
NIST Handbook 143 97 March 2003

4.1.5 The laboratory shall: 

____ a) have managerial and technical personnel with the authority and resources needed to carry out 

their duties and to identify the occurrence of departures from the quality system or from the 

procedures for performing tests and/or calibrations, and to initiate actions to prevent or 

minimize such departures (see also 5.2); 

____ b) have arrangements to ensure that its management and personnel are free from any undue 

internal and external commercial, financial and other pressures and influences that may 

adversely affect the quality of their work; 

____ c) have policies and procedures to ensure the protection of its clients' confidential information 

and proprietary rights, including procedures for protecting the electronic storage and 

transmission of results; 

____ d) have policies and procedures to avoid involvement in any activities that would diminish 

confidence in its competence, impartiality, judgement or operational integrity; 

 

____ e) define the organization and management structure of the laboratory, its place in any 

parent organization, and the relationships between quality management, technical 

operations and support services; 

 

____ f) Specify the responsibility, authority and interrelationships of all personnel who 

manage, perform or verify work affecting the quality of the tests and/or calibrations;

 

____ g) Provide adequate supervision of testing and calibration staff, including trainees, by 

persons familiar with methods and procedures, purpose of each test and/or 

calibration, and with the assessment of the test or calibration results; 

____ h) have technical management which has overall responsibility for the technical 

operations and the provision of the resources needed to ensure the required quality of 

laboratory operations; 

 Name of person: __________________________________________________ 

 Area of responsibility: ______________________________________________ 

 Repeat as necessary: ______________________________________________ 

____ i) Appoint a member of staff as quality manager (however named) who, irrespective of 

other duties and responsibilities, shall have defined responsibility and authority for 

ensuring that the quality system is implemented and followed at all times; the quality 

manager shall have direct access to the highest level of management at which 

decisions are made on laboratory policy or resources; 

 

____ j) 

Name of person: __________________________________________________ 

appoint deputies for key managerial personnel (see note). 

 

 Name(s): ________________________________________________________ 
NIST Handbook 143 98 March 2003

NOTE Individuals may have more than one function and it may be impractical to appoint deputies 

for every function. 

4.2 Quality system 

 4.2.1 

 

____ a) The laboratory shall establish, implement and maintain a quality system appropriate 

to the scope of its activities. 

 

____ b) The laboratory shall document its policies, systems, programs, procedures and 

instructions to the extent necessary to assure the quality of the test and/or calibration 

results. 

____ c) The system’s documentation shall be communicated to, understood by, available to, 

and implemented by the appropriate personnel. 

____ 4.2.2 The laboratory’s quality system policies and objectives shall be defined in a quality manual 

(however named). The overall objectives shall be documented in a quality policy statement. 

The quality policy statement shall be issued under the authority of the chief executive. It 

shall include at least the following: 

 

____ a) the laboratory management's commitment to good professional practice and to the quality of 

its testing and calibration in servicing its clients; 

 

___F b) the management’s statement of the laboratory's standard of service; 

 

____ c) the objectives of the quality system; 

 

____ d) a requirement that all personnel concerned with testing and calibration activities within the 

laboratory familiarize themselves with the quality documentation and implement the policies 

and procedures in their work; and 

 

____ e) the laboratory management's commitment to compliance with this Handbook. 

 

NOTE The quality policy statement should be concise and may include the requirement that tests 

and/or calibrations shall always be carried out in accordance with stated methods and clients' 

requirements. When the test and/or calibration laboratory is part of a larger organization, some 

quality policy elements may be in other documents. 

 4.2.3 

____ a) The quality manual shall include or make reference to the supporting procedures including 

technical procedures. 

 

___F b) It shall outline the structure of the documentation used in the quality system. 

____ 4.2.4 The roles and responsibilities of technical management and the quality manager, including 

their responsibility for ensuring compliance with this Handbook, shall be defined in the 

quality manual. 
NIST Handbook 143 99 March 2003

4.3 Document control 

 4.3.1 General 

____ The laboratory shall establish and maintain procedures to control all documents that form part of its 

quality system (internally generated or from external sources), such as regulations, standards, other 

normative documents, test and/or calibration methods, as well as drawings, software, specifications, 

instructions and manuals. 

NOTE 1 In this context "document" could be policy statements, procedures, specifications, 

calibration tables, charts, text books, posters, notices, memoranda, software, drawings, plans, etc. 

These may be on various media, whether hard copy or electronic, and they may be digital, analog, 

photographic or written. 

 

NOTE 2 The control of data related to testing and calibration is covered in 5.4.7. The control of 

records is covered in 4.12. 

 4.3.2 Document approval and issue 

 4.3.2.1 

___F a) All documents issued to personnel in the laboratory as part of the quality system shall be 

reviewed and approved for use by authorized personnel prior to issue. 

 

___F b) A master list or an equivalent document control procedure identifying the current revision 

status and distribution of documents in the quality system shall be established and be readily 

available to preclude the use of invalid and/or obsolete documents. 

 4.3.2.2 The procedure(s) adopted shall ensure that: 

___F a) authorized editions of appropriate documents are available at all locations where operations 

essential to the effective functioning of the laboratory are performed; 

 

___F b) documents are periodically reviewed and, where necessary, revised to ensure continuing 

suitability and compliance with applicable requirements; 

 

___F c) invalid or obsolete documents are promptly removed from all points of issue or use, or 

otherwise assured against unintended use; 

 

___F d) obsolete documents retained for either legal or knowledge preservation purposes are suitably 

marked. 

4.3.2.3 Quality system documents generated by the laboratory shall be uniquely identified. 

Such identification shall include: 

___F a) the date of issue and/or revision identification, 

 

___F b) page numbering, 

 

___F c) the total number of pages or a mark to signify the end of the document, and 

 

___F d) the issuing authority(ies). 

 4.3.3 Document changes 
NIST Handbook 143 100 March 2003

___F 4.3.3.1 Changes to documents shall be reviewed and approved by the same function that 

performed the original review unless specifically designated otherwise. The designated 

personnel shall have access to pertinent background information upon which to base 

their review and approval.

 

___F 4.3.3.2 Where practicable, the altered or new text shall be identified in the document or the 

appropriate attachments. 

 

4.3.3.3 

___F a) If the laboratory's documentation control system allows for the amendment of documents by 

hand pending the reissue of the documents, the procedures and authorities for such 

amendments shall be defined. 

 

___F b) Amendments shall be clearly marked, initialed and dated. A revised document shall be 

formally reissued as soon as practicable. 

___F 4.3.3.4 Procedures shall be established to describe how changes in documents maintained in 

computerized systems are made and controlled. 

 

4.4 Review of requests, tenders and contracts 

____ 4.4.1 The laboratory shall establish and maintain procedures for the review of requests, tenders 

and contracts. The policies and procedures for these reviews leading to a contract for testing 

and/or calibration shall ensure that: 

___F a) the requirements, including the methods to be used, are adequately defined, documented and 

understood (see 5.4.2); 

 

____ b) the laboratory has the capability and resources to meet the requirements; 

 

___F c) the appropriate test and/or calibration method is selected and capable of meeting the clients' 

requirements (see 5.4.2). 

___F d) Any differences between the request or tender and the contract shall be resolved before any 

work commences. Each contract shall be acceptable both to the laboratory and the client. 

NOTE 1 The request, tender and contract review should be conducted in a practical and efficient 

manner, and the effect of financial, legal and time schedule aspects should be taken into account. For 

internal clients, reviews of requests, tenders and contracts can be performed in a simplified way. 

 

NOTE 2 The review of capability should establish that the laboratory possesses the necessary 

physical, personnel and information resources, and that the laboratory's personnel have the skills and 

expertise necessary for the performance of the tests and/or calibrations in question. The review may 

also encompass results of earlier participation in interlaboratory comparisons or proficiency testing 

and/or the running of trial test or calibration programs using samples or items of known value in 

order to determine uncertainties of measurement, limits of detection, confidence limits, etc. 

 

NOTE 3 A contract may be any written or oral agreement to provide a client with testing and/or 

calibration services. 
NIST Handbook 143 101 March 2003

___F 4.4.2 Records of reviews, including any significant changes, shall be maintained. Records shall 

also be maintained of pertinent discussions with a client relating to the client's requirements 

or the results of the work during the period of execution of the contract. 

NOTE For review of routine and other simple tasks, the date and the identification (e.g., the 

initials) of the person in the laboratory responsible for carrying out the contracted work are 

considered adequate. For repetitive routine tasks, the review need be made only at the initial enquiry 

stage or on granting of the contract for ongoing routine work performed under a general agreement 

with the client, provided that the client's requirements remain unchanged. For new, complex or 

advanced testing and/or calibration tasks, a more comprehensive record should be maintained. 

___F 4.4.3 The review shall also cover any work that is subcontracted by the laboratory. 

 

___F 4.4.4 The client shall be informed of any deviation from the contract. 

 

___F 4.4.5 If a contract needs to be amended after work has commenced, the same contract review 

process shall be repeated and any amendments shall be communicated to all affected 

personnel. 

4.5 Subcontracting of tests and calibrations 

____ 4.5.1 When a laboratory subcontracts work whether because of unforeseen reasons (e.g., 

workload, need for further expertise or temporary incapacity) or on a continuing basis (e.g., 

through permanent subcontracting, agency or franchising arrangements), this work shall be 

placed with a competent subcontractor. A competent subcontractor is one that, for example, 

complies with this Handbook for the work in question. 

 

____ 4.5.2 The laboratory shall advise the client of the arrangement in writing and, when appropriate, 

gain the approval of the client, preferably in writing. 

 

___F 4.5.3 The laboratory is responsible to the client for the subcontractor’s work, except in the case 

where the client or a regulatory authority specifies which subcontractor is to be used. 

 

____ 4.5.4 The laboratory shall maintain a register of all subcontractors that it uses for tests and/or 

calibrations and a record of the evidence of compliance with this Handbook for the work in 

question. 

4.6 Purchasing services and supplies 

____ 4.6.1 The laboratory shall have a policy and procedure(s) for the selection and purchasing of 

services and supplies it uses that affect the quality of the tests and/or calibrations. 

Procedures shall exist for the purchase, reception and storage of reagents and laboratory 

consumable materials relevant for the tests and calibrations. 

 4.6.2 

____ a) The laboratory shall ensure that purchased supplies and reagents and consumable materials 

that affect the quality of tests and/or calibrations are not used until they have been inspected 

or otherwise verified as complying with standard specifications or requirements defined in 

the methods for the tests and/or calibrations concerned. These services and supplies used 

shall comply with specified requirements. 
NIST Handbook 143 102 March 2003

 

____ b) Records of actions taken to check compliance shall be maintained. 

 

____ 4.6.3 Purchasing documents for items affecting the quality of laboratory output shall contain data 

describing the services and supplies ordered. These purchasing documents shall be reviewed 

and approved for technical content prior to release. 

NOTE The description may include type, class, grade, precise identification, specifications, 

drawings, inspection instructions, other technical data including approval of test results, the quality 

required and the quality system standard under which they were made. 

4.6.4 

 

____ a) The laboratory shall evaluate suppliers of critical consumables, supplies and services which 

affect the quality of testing and calibration, and 

 

____ b) shall maintain records of these evaluations and list those approved. 

4.7 Service to the client 

 

___F The laboratory shall afford clients or their representatives cooperation to clarify the client's request 

and to monitor the laboratory's performance in relation to the work performed, provided that the 

laboratory ensures confidentiality to other clients. 

NOTE 1 Such cooperation may include: 

 

 a) providing the client or the client's representative reasonable access to relevant areas of the 

laboratory for the witnessing of tests and/or calibrations performed for the client; 

 

 b) preparation, packaging, and dispatch of test and/or calibration items needed by the client for 

verification purposes. 

 

 

 NOTE 2 Such cooperation may include: Clients value the maintenance of good communication, 

advice and guidance in technical matters, and opinions and interpretations based on results. 

Communication with the client, especially in large assignments, should be maintained throughout the 

work. The laboratory should inform the client of any delays or major deviations in the performance 

of the tests and/or calibrations. 

 NOTE 3 Laboratories are encouraged to obtain other feedback, both positive and negative, from 

their clients (e.g., client surveys). The feedback should be used to improve the quality system, 

testing and calibration activities and client service. 

4.8 Complaints 

____ 4.8.1 The laboratory shall have a policy and procedure for the resolution of complaints received 

from clients or other parties. 

 

____ 4.8.2 Records shall be maintained of all complaints and of the investigations and corrective 

actions taken by the laboratory (see also 4.10). 

4.9 Control of non-conforming testing and/or calibration work 
NIST Handbook 143 103 March 2003

____ 4.9.1 The laboratory shall have a policy and procedures that shall be implemented when any aspect 

of its testing and/or calibration work, or the results of this work, do not conform to its own 

procedures or the agreed requirements of the client. The policy and procedures shall ensure 

that: 

 

___F a) the responsibilities and authorities for the management of non-conforming work are 

designated and actions (including halting of work and withholding of test reports and 

calibration certificates, as necessary) are defined and taken when non-conforming work is 

identified; 

 

____ b) an evaluation of the significance of the non-conforming work is made; 

 

___F c) corrective actions are taken immediately, together with any decision about the acceptability 

of the non-conforming work; 

 

____ d) where necessary, the client is notified and work is recalled; 

 

___F e) the responsibility for authorizing the resumption of work is defined. 

 

NOTE Identification of non-conforming work or problems with the quality system or with testing 

and/or calibration activities can occur at various places within the quality system and technical 

operations. Examples are customer complaints, quality control, instrument calibration, checking of 

consumable materials, staff observations or supervision, test report and calibration certificate 

checking, management reviews and internal or external audits. 

___F 4.9.2 Where the evaluation indicates that the non-conforming work could recur or that there is 

doubt about the compliance of the laboratory's operations with its own policies and 

procedures, the corrective action procedures given in 4.10 shall be promptly followed. 

4.10 Corrective action 

 4.10.1 General 

____ The laboratory shall establish a policy and procedure and shall designate appropriate authorities for 

implementing corrective action when non-conforming work or departures from the policies and 

procedures in the quality system or technical operations have been identified. 

 

NOTE A problem with the quality system or with the technical operations of the laboratory may be 

identified through a variety of activities, such as control of non-conforming work, internal or external 

audits, management reviews, feedback from clients or staff observations. 

 4.10.2 Cause analysis 

___F The procedure for corrective action shall start with an investigation to determine the root cause(s) of 

the problem. 

 

NOTE Cause analysis is the key and sometimes the most difficult part in the corrective action 

procedure. Often the root cause is not obvious and thus a careful analysis of all potential causes of 

the problem is required. Potential causes could include client requirements, the samples, sample 

specifications, methods and procedures, staff skills and training, consumables, or equipment and its 

calibration. 

 4.10.3 Selection and implementation of corrective actions 
NIST Handbook 143 104 March 2003

___F a) Where corrective action is needed, the laboratory shall identify potential corrective actions. 

It shall select and implement the action(s) most likely to eliminate the problem and to 

prevent recurrence. 

___F b) Corrective actions shall be to a degree appropriate to the magnitude and the risk of the 

problem. 

 

___F c) The laboratory shall document and implement any required changes resulting from 

corrective action investigations. 

 4.10.4 Monitoring of corrective actions 

___F The laboratory shall monitor the results to ensure that the corrective actions taken have been 

effective. 

 4.10.5 Additional audits 

____ Where the identification of non-conformances or departures casts doubts on the laboratory's 

compliance with its own policies and procedures, or on its compliance with this Handbook, the 

laboratory shall ensure that the appropriate areas of activity are audited in accordance with 4.13 as 

soon as possible. 

NOTE Such additional audits often follow the implementation of the corrective actions to confirm 

their effectiveness. An additional audit should be necessary only when a serious issue or risk to the 

business is identified. 

4.11 Preventive action 

 4.11.1 

___F a) Needed improvements and potential sources of non-conformances, either technical or 

concerning the quality system, shall be identified. 

 

___F b) If preventive action is required, action plans shall be developed, implemented and monitored 

to reduce the likelihood of the occurrence of such non-conformances and to take advantage 

of the opportunities for improvement. 

 

___F 4.11.2 Procedures for preventive actions shall include the initiation of such actions and 

application of controls to ensure that they are effective. 

 NOTE 1 Preventive action is a proactive process to identify opportunities for improvement rather 

than a reaction to the identification of problems or complaints. 

NOTE 2 Apart from the review of the operational procedures, the preventive action might involve 

analysis of data, including trend and risk analyses and proficiency-testing results. 

 

4.12 Control of records 

 4.12.1 General 
NIST Handbook 143 105 March 2003

____ 4.12.1.1 The laboratory shall establish and maintain procedures for identification, collection, 

indexing, access, filing, storage, maintenance and disposal of quality and technical 

records. Quality records shall include reports from internal audits and management 

reviews as well as records of corrective and preventive actions. 

 4.12.1.2 

____ a) All records shall be legible and shall be stored and retained in such a way that they are 

readily retrievable in facilities that provide a suitable environment to prevent damage or 

deterioration and to prevent loss. 

 

____ b) Retention times of records shall be established. 

NOTE Records may be in any media, such as hard copy or electronic media. 

 

____ 4.12.1.3 All records shall be held secure and in confidence. 

 

____ 4.12.1.4 The laboratory shall have procedures to protect and back up records stored electronically 

and to prevent unauthorized access to or amendment of these records. 

 4.12.2 Technical records 

 4.12.2.1 

____ a) The laboratory shall retain records of original observations, derived data and sufficient 

information to establish an audit trail, calibration records, staff records and a copy of each 

test report or calibration certificate issued, for a defined period. 

 

____ b) The records for each test or calibration shall contain sufficient information to facilitate, if 

possible, identification of factors affecting the uncertainty and to enable the test or 

calibration to be repeated under conditions as close as possible to the original. 

 

____ c) The records shall include the identity of personnel responsible for the sampling, performance 

of each test and/or calibration and checking of results. 

 NOTE 1 In certain fields it may be impossible or impracticable to retain records of all original 

observations. 

 

 NOTE 2 Technical records are accumulations of data (see 5.4.7) and information which result from 

carrying out tests and/or calibrations and which indicate whether specified quality or process 

parameters are achieved. They may include forms, contracts, work sheets, work books, check sheets, 

work notes, control graphs, external and internal test reports and calibration certificates, clients' 

notes, papers and feedback. 

___F 4.12.2.2 Observations, data and calculations shall be recorded at the time they are made and shall 

be identifiable to the specific task. 

 4.12.2.3 

___F a) When mistakes occur in records, each mistake shall be crossed out, not erased, made illegible 

or deleted, and the correct value entered alongside. All such alterations to records shall be 

signed or initialed by the person making the correction. 

 
NIST Handbook 143 106 March 2003

____ b) In the case of records stored electronically, equivalent measures shall be taken to avoid loss 

or change of original data. 

4.13 Internal audits 

 4.13.1 

____ a) The laboratory shall periodically, and in accordance with a predetermined schedule and 

procedure, conduct internal audits of its activities to verify that its operations continue to 

comply with the requirements of the quality system and this Handbook. The internal audit 

program shall address all elements of the quality system, including the testing and/or 

calibration activities. It is the responsibility of the quality manager to plan and organize 

audits as required by the schedule and requested by management. 

 

____ b) Such audits shall be carried out by trained and qualified personnel who are, wherever 

resources permit, independent of the activity to be audited. 

NOTE The cycle for internal auditing should normally be completed in one year. 

____ 4.13.2 When audit findings cast doubt on the effectiveness of the operations or on the correctness or 

validity of the laboratory's test or calibration results, the laboratory shall take timely 

corrective action, and shall notify clients in writing if investigations show that the laboratory 

results may have been affected. 

 

____ 4.13.3 The area of activity audited, the audit findings and corrective actions that arise from them 

shall be recorded. 

 

____ 4.13.4 Follow-up audit activities shall verify and record the implementation and effectiveness of the 

corrective action taken. 

 

4.14 Management reviews 

____ 4.14.1 In accordance with a predetermined schedule and procedure, the laboratory's executive 

management shall periodically conduct a review of the laboratory's quality system and 

testing and/or calibration activities to ensure their continuing suitability and effectiveness, 

and to introduce necessary changes or improvements. The review shall take account of:

 

___F a) the suitability of policies and procedures; 

 

___F b) reports from managerial and supervisory personnel; 

 

___F c) the outcome of recent internal audits; 

 

___F d) corrective and preventive actions; 

 

___F e) assessments by external bodies; 

 

___F f) the results of interlaboratory comparisons or proficiency tests; 

 

___F g) changes in the volume and type of the work; 

 

___F h) client feedback; 
NIST Handbook 143 107 March 2003

 

___F i) complaints; 

 

___F j) other relevant factors, such as quality control activities, resources and staff training. 

 NOTE 1 A typical period for conducting a management review is once every 12 months. 

 

 NOTE 2 Results should feed into the laboratory planning system and should include the goals, 

objectives and action plans for the coming year. 

 

 NOTE 3 A management review includes consideration of related subjects at regular management 

meetings. 

 4.14.2 

____ a) Findings from management reviews and the actions that arise from them shall be recorded. 

 

____ b) The management shall ensure that those actions are carried out within an appropriate and 

agreed timescale. 

5 Technical requirements for accreditation 

5.1 General 

 5.1.1 Many factors determine the correctness and reliability of the tests and/or calibrations 

performed by a laboratory. These factors include contributions from: 

 

• human factors (5.2); 

 

• accommodation and environmental conditions (5.3); 

 

• test and calibration methods and method validation (5.4); 

 

• equipment (5.5); 

 

• measurement traceability (5.6 and Annex B); 

 

• sampling (5.7); 

 

• the handling of test and calibration items (5.8). 

 

___F 5.1.2 The extent to which the factors contribute to the total uncertainty of measurement differs 

considerably between (types of) tests and between (types of) calibrations. The laboratory 

shall take account of these factors in developing test and calibration methods and procedures, 

in the training and qualification of personnel, and in the selection and calibration of the 

equipment it uses. 

5.2 Personnel 

 5.2.1 
NIST Handbook 143 108 March 2003

____ a) The laboratory management shall ensure the competence of all who operate specific 

equipment, perform tests and/or calibrations, evaluate results, and sign test reports and 

calibration certificates. 

 

____ b) When using staff who are undergoing training, appropriate supervision shall be provided. 

Personnel performing specific tasks shall be qualified on the basis of appropriate education, 

training, experience and/or demonstrated skills, as required. 

 NOTE 1 In some technical areas (e.g., nondestructive testing) it may be required that the personnel 

performing certain tasks hold personnel certification. The laboratory is responsible for fulfilling 

specified personnel certification requirements. The requirements for personnel certification might be 

regulatory, included in the standards for the specific technical field, or required by the client. 

 

NOTE 2 The personnel responsible for the opinions and interpretation included in test reports 

should, in addition to the appropriate qualifications, training, experience and satisfactory knowledge 

of the testing carried out, also have: 

 

• relevant knowledge of the technology used for the manufacturing of the items, materials, 

products, etc. tested, or the way they are used or intended to be used, and of the defects or 

degradations which may occur during or in service; 

 

• knowledge of the general requirements expressed in the legislation and standards; and 

 

• an understanding of the significance of deviations found with regard to the normal use of the 

items, materials, products, etc. concerned. 

____ 5.2.2 The management of the laboratory shall formulate the goals with respect to the education, 

training and skills of the laboratory personnel. The laboratory shall have a policy and 

procedures for identifying training needs and providing training of personnel. The training 

program shall be relevant to the present and anticipated tasks of the laboratory. 

 5.2.3 

___F a) The laboratory shall use personnel who are employed by, or under contract to, the laboratory. 

 

 

___F b) Where contracted and additional technical and key support personnel are used, the laboratory 

shall ensure that such personnel are supervised and competent and that they work in 

accordance with the laboratory's quality system. 

____ 5.2.4 The laboratory shall maintain current job descriptions for managerial, technical and key 

support personnel involved in tests and/or calibrations. 

NOTE Job descriptions can be defined in many ways. As a minimum, the following should be 

defined: 

 

• the responsibilities with respect to performing tests and/or calibrations; 

 

• the responsibilities with respect to the planning of tests and/or calibrations and evaluation of 

results; 

 

• the responsibilities for reporting opinions and interpretations; 

 
NIST Handbook 143 109 March 2003

• the responsibilities with respect to method modification and development and validation of 

new methods; 

 

• expertise and experience required; 

 

• qualifications and training programs; 

 

• managerial duties. 

 5.2.5

 

 

___F a) The management shall authorize specific personnel to perform particular types of sampling, 

test and/or calibration, to issue test reports and calibration certificates, to give opinions and 

interpretations and to operate particular types of equipment. 

 

____ b) The laboratory shall maintain records of the relevant authorization(s), competence, 

educational and professional qualifications, training, skills and experience of all technical 

personnel, including contracted personnel. 

 

___F c) This information shall be readily available and shall include the date on which authorization 

and/or competence is confirmed. 

 

 WMD Note: This requirement also applies to Approved Signatories. 

5.3 Accommodation and environmental conditions 

 5.3.1 

____ Laboratory facilities for testing and/or calibration, including but not limited to energy 

sources, lighting and environmental conditions, shall be such as to facilitate correct 

performance of the tests and/or calibrations. 

The laboratory shall ensure that the environmental conditions do not invalidate the results or 

adversely affect the required quality of any measurement. Particular care shall be taken 

when sampling and tests and/or calibrations are undertaken at sites other than a permanent 

laboratory facility. 

 

___F b) The technical requirements for accommodation and environmental conditions that can affect 

the results of tests and calibrations shall be documented. 

 5.3.2 

____ a) The laboratory shall monitor, control and record environmental conditions as required by the 

relevant specifications, methods and procedures or where they influence the quality of the 

results. Due attention shall be paid, for example, to biological sterility, dust, electromagnetic 

disturbances, radiation, humidity, electrical supply, temperature, and sound and vibration 

levels, as appropriate to the technical activities concerned. 

 

____ b) Tests and calibrations shall be stopped when the environmental conditions jeopardize the 

results of the tests and/or calibrations. 
NIST Handbook 143 110 March 2003

____ 5.3.3 There shall be effective separation between neighboring areas in which there are 

incompatible activities. Measures shall be taken to prevent cross-contamination. 

 

 

____ 5.3.4 Access to and use of areas affecting the quality of the tests and/or calibrations shall be 

controlled. The laboratory shall determine the extent of control based on its particular 

circumstances. 

 

____ 5.3.5 Measures shall be taken to ensure good housekeeping in the laboratory. Special procedures 

shall be prepared where necessary. 

5.4 Test and calibration methods and method validation 

 5.4.1 General 

____ a) The laboratory shall use appropriate methods and procedures for all tests and/or calibrations 

within its scope. These include sampling, handling, transport, storage and preparation of 

items to be tested and/or calibrated, and, where appropriate, an estimation of the 

measurement uncertainty as well as statistical techniques for analysis of test and/or 

calibration data. 

 

____ b) The laboratory shall have instructions on the use and operation of all relevant equipment, and 

on the handling and preparation of items for testing and/or calibration, or both, where the 

absence of such instructions could jeopardize the results of tests and/or calibrations. 

 

____ c) All instructions, standards, manuals and reference data relevant to the work of the laboratory 

shall be kept up to date and shall be made readily available to personnel (see 4.3). 

 

____ d) Deviation from test and calibration methods shall occur only if the deviation has been 

documented, technically justified, authorized, and accepted by the client. 

NOTE International, regional or national standards or other recognized specifications that contain 

sufficient and concise information on how to perform the tests and/or calibrations do not need to be 

supplemented or rewritten as internal procedures if these standards are written in a way that they can 

be used as published by the operating staff in a laboratory. It may be necessary to provide additional 

documentation for optional steps in the method or additional details. 

 5.4.2 Selection of methods 

____ a) The laboratory shall use test and/or calibration methods, including methods for sampling, 

which meet the needs of the client and which are appropriate for the tests and/or calibrations 

it undertakes. Methods published in international, regional or national standards shall 

preferably be used. The laboratory shall ensure that it uses the latest valid edition of a 

standard unless it is not appropriate or possible to do so. 

 

___F b) When necessary, the standard shall be supplemented with additional details to ensure 

consistent application. 

 

____ c) When the client does not specify the method to be used, the laboratory shall select 

appropriate methods that have been published either in international, regional or national 

standards, or by reputable technical organizations, or in relevant scientific texts or journals, 

or as specified by the manufacturer of the equipment. Laboratory-developed methods or 

methods adopted by the laboratory may also be used if they are appropriate for the intended 
NIST Handbook 143 111 March 2003

use and if they are validated. 

 

___F d) The client shall be informed as to the method chosen. 

 

___F e) The laboratory shall confirm that it can properly operate standard methods before 

introducing the tests or calibrations. If the standard method changes, the confirmation shall 

be repeated. 

 

___F f) The laboratory shall inform the client when the method proposed by the client is considered 

to be inappropriate or out of date. 

 5.4.3 Laboratory-developed methods 

___F a) The introduction of test and calibration methods developed by the laboratory for its own use 

shall be a planned activity and shall be assigned to qualified personnel equipped with 

adequate resources. 

 

___F b) Plans shall be updated as development proceeds and effective communication amongst all 

personnel involved shall be ensured. 

 5.4.4 Non-standard methods 

____ a) When it is necessary to use methods not covered by standard methods, these shall be subject 

to agreement with the client and shall include a clear specification of the client's 

requirements and the purpose of the test and/or calibration. 

 

____ b) The method developed shall have been validated appropriately before use. 

NOTE For new test and/or calibration methods, procedures should be developed prior to the tests 

and/or calibrations being performed and should contain at least the following information: 

 

 a) appropriate identification; 

 

 b) scope; 

 

 c) description of the type of item to be tested or calibrated; 

 

 d) parameters or quantities and ranges to be determined; 

 

 e) apparatus and equipment, including technical performance requirements; 

 

 f) reference standards and reference materials required; 

 

 g) environmental conditions required and any stabilization period needed; 

 

 h) description of the procedure, including: 

 

• affixing of identification marks, handling, transporting, storing and preparation of items,

 • checks to be made before the work is started, 

 

• checks that the equipment is working properly and, where required, calibration and 

adjustment of the equipment before each use, 
NIST Handbook 143 112 March 2003

 

• the method of recording the observations and results, 

 

• any safety measures to be observed; 

 i) criteria and/or requirements for approval/rejection; 

 

 j) data to be recorded and method of analysis and presentation; 

 

 k) the uncertainty or the procedure for estimating uncertainty. 

 5.4.5 Validation of methods 

 5.4.5.1 Validation is the confirmation by examination and the provision of objective evidence that 

the particular requirements for a specific intended use are fulfilled. 

 5.4.5.2 

____ a) The laboratory shall validate non-standard methods, laboratory-designed/developed methods, 

standard methods used outside their intended scope, and amplifications and modifications of 

standard methods to confirm that the methods are fit for the intended use. The validation 

shall be as extensive as is necessary to meet the needs of the given application or field of 

application. 

 

___F b) The laboratory shall record the results obtained, the procedure used for the validation, and a 

statement as to whether the method is fit for the intended use. 

NOTE 1 Validation may include procedures for sampling, handling and transportation. 

NOTE 2 The techniques used for the determination of the performance of a method should be one of, 

or a combination of, the following: 

 

• calibration using reference standards or reference materials; 

 

• comparison of results achieved with other methods; 

 

• interlaboratory comparisons; 

 

• systematic assessment of the factors influencing the result; 

 

• assessment of the uncertainty of the results based on scientific understanding of the 

theoretical principles of the method and practical experience. 

NOTE 3 When some changes are made in the validated non-standard methods, the influence of such 

changes should be documented and, if appropriate, a new validation should be carried out. 

___F 5.4.5.3 The range and accuracy of the values obtainable from validated methods (e.g., the 

uncertainty of the results, detection limit, selectivity of the method, linearity, limit of 

repeatability and/or reproducibility, robustness against external influences and/or crosssensitivity against interference from the matrix of the sample/test object), as assessed for 

the intended use, shall be relevant to the clients' needs.

 

 NOTE 1 Validation includes specification of the requirements, determination of the characteristics 
NIST Handbook 143 113 March 2003

of the methods, a check that the requirements can be fulfilled by using the method, and a statement 

on the validity. 

 

 NOTE 2 As method-development proceeds, regular review should be carried out to verify that the 

needs of the client are still being fulfilled. Any change in requirements requiring modifications to the 

development plan should be approved and authorized. 

 NOTE 3 Validation is always a balance between costs, risks and technical possibilities. There are 

many cases in which the range and uncertainty of the values (e.g., accuracy, detection limit, 

selectivity, linearity, repeatability, reproducibility, robustness and cross-sensitivity) can only be 

given in a simplified way due to lack of information. 

 5.4.6 Estimation of uncertainty of measurement 

____ 5.4.6.1 A calibration laboratory, or a testing laboratory performing its own calibrations, shall have 

and shall apply a procedure to estimate the uncertainty of measurement for all calibrations 

and types of calibrations.

 

___F 5.4.6.2 Testing laboratories shall have and shall apply procedures for estimating uncertainty of 

measurement. In certain cases the nature of the test method may preclude rigorous, 

metrologically and statistically valid, calculation of uncertainty of measurement. In these 

cases the laboratory shall at least attempt to identify all the components of uncertainty and 

make a reasonable estimation, and shall ensure that the form of reporting of the result does 

not give a wrong impression of the uncertainty. Reasonable estimation shall be based on 

knowledge of the performance of the method and on the measurement scope and shall 

make use of, for example, previous experience and validation data. 

NOTE 1 The degree of rigor needed in an estimation of uncertainty of measurement depends on 

factors such as: 

 

• the requirements of the test method; 

 

 • the requirements of the client; 

 

• the existence of narrow limits on which decisions on conformance to a specification are 

based. 

NOTE 2 In those cases where a well recognized test method specifies limits to the values of the 

major sources of uncertainty of measurement and specifies the form of presentation of calculated 

results, the laboratory is considered to have satisfied this clause by following the test method and 

reporting instructions (see 5.10). 

____ 5.4.6.3 When estimating the uncertainty of measurement, all uncertainty components which are of 

importance in the given situation shall be taken into account using appropriate methods of 

analysis. 

 

 NOTE 1 Sources contributing to the uncertainty include, but are not necessarily limited to, the 

reference standards and reference materials used, methods and equipment used, environmental 

conditions, properties and condition of the item being tested or calibrated, and the operator. 

 

 NOTE 2 The predicted long-term behavior of the tested and/or calibrated item is not normally taken 

into account when estimating the measurement uncertainty. 
NIST Handbook 143 114 March 2003

 

 NOTE 3 For further information, see ISO 5725 and the Guide to the Expression of Uncertainty in 

Measurement (see 1.4). 

 

 WMD Note: ANSI/NCSL Z540-2-1997 and NIST Technical Note 1297, 1994 edition, are 

considered to be equivalent to the Guide to the Expression of Uncertainty in Measurement (GUM).

 5.4.7 Control of data 

____ 5.4.7.1 Calculations and data transfers shall be subject to appropriate checks in a systematic 

manner.

5.4.7.2 When computers or automated equipment are used for the acquisition, processing, 

recording, reporting, storage or retrieval of test or calibration data, the laboratory shall 

ensure that: 

____ a) computer software developed by the user is documented in sufficient detail and is suitably 

validated as being adequate for use; 

 

____ b) procedures are established and implemented for protecting the data; such procedures shall 

include, but not be limited to, integrity and confidentiality of data entry or collection, data 

storage, data transmission and data processing; 

 

____ c) computers and automated equipment are maintained to ensure proper functioning and are 

provided with the environmental and operating conditions necessary to maintain the integrity 

of test and calibration data. 

 

NOTE Commercial off-the-shelf software (e.g., word processing, database and statistical 

programs) in general use within their designed application range may be considered to be 

sufficiently validated. However, laboratory software configuration/modifications should be 

validated as in 5.4.7.2a). 

5.5 Equipment 

 5.5.1 

____ a) The laboratory shall be furnished with all items of sampling, measurement and test 

equipment required for the correct performance of the tests and/or calibrations (including 

sampling, preparation of test and/or calibration items, processing and analysis of test and/or 

calibration data). 

 

____ b) In those cases where the laboratory needs to use equipment outside its permanent control, it 

shall ensure that the requirements of this Handbook are met. 

 5.5.2 

____ a) Equipment and its software used for testing, calibration and sampling shall be capable of 

achieving the accuracy required and shall comply with specifications relevant to the tests 

and/or calibrations concerned. 

 

____ b) Calibration programs shall be established for key quantities or values of the instruments 

where these properties have a significant effect on the results. 

 
NIST Handbook 143 115 March 2003

____ c) Before being placed into service, equipment (including that used for sampling) shall be 

calibrated or checked to establish that it meets the laboratory's specification requirements and 

complies with the relevant standard specifications. It shall be checked and/or calibrated 

before use (see 5.6). 

____ 5.5.3 Equipment shall be operated by authorized personnel. Up-to-date instructions on the use and 

maintenance of equipment (including any relevant manuals provided by the manufacturer of 

the equipment) shall be readily available for use by the appropriate laboratory personnel. 

 

____ 5.5.4 Each item of equipment and its software used for testing and calibration and significant to 

the result shall, when practicable, be uniquely identified. 

 

____ 5.5.5 Records shall be maintained of each item of equipment and its software significant to the 

tests and/or calibrations performed. The records shall include at least the following: 

____ a) the identity of the item of equipment and its software; 

 

____ b) the manufacturer's name, type identification, and serial number or other unique 

identification; 

 

____ c) checks that equipment complies with the specification (see 5.5.2); 

 

____ d) the current location, where appropriate; 

 

____ e) the manufacturer's instructions, if available, or reference to their location; 

____ f) dates, results and copies of reports and certificates of all calibrations, adjustments, 

acceptance criteria, and the due date of next calibration; 

 

____ g) the maintenance plan, where appropriate, and maintenance carried out to date; 

 

____ h) any damage, malfunction, modification or repair to the equipment. 

____ 5.5.6 The laboratory shall have procedures for safe handling, transport, storage, use and planned 

maintenance of measuring equipment to ensure proper functioning and in order to prevent 

contamination or deterioration. 

NOTE Additional procedures may be necessary when measuring equipment is used outside the 

permanent laboratory for tests, calibrations or sampling. 

 

 5.5.7 

____ a) Equipment that has been subjected to overloading or mishandling, gives suspect results, or 

has been shown to be defective or outside specified limits, shall be taken out of service. It 

shall be isolated to prevent its use or clearly labeled or marked as being out of service until it 

has been repaired and shown by calibration or test to perform correctly. 

 

____ b) The laboratory shall examine the effect of the defect or departure from specified limits on 

previous tests and/or calibrations and shall institute the "Control of non-conforming work" 

procedure (see 4.9). 

____ 5.5.8 Whenever practicable, all equipment under the control of the laboratory and requiring 

calibration shall be labeled, coded or otherwise identified to indicate the status of calibration, 
NIST Handbook 143 116 March 2003

including the date when last calibrated and the date or expiration criteria when recalibration 

is due. 

 

____ 5.5.9 When, for whatever reason, equipment goes outside the direct control of the laboratory, the 

laboratory shall ensure that the function and calibration status of the equipment are checked 

and shown to be satisfactory before the equipment is returned to service. 

___F 5.5.10 When intermediate checks are needed to maintain confidence in the calibration status of 

the equipment, these checks shall be carried out according to a defined procedure. 

 

___F 5.5.11 Where calibrations give rise to a set of correction factors, the laboratory shall have 

procedures to ensure that copies (e.g., in computer software) are correctly updated. 

 

____ 5.5.12 Test and calibration equipment, including both hardware and software, shall be 

safeguarded from adjustments which would invalidate the test and/or calibration results.

5.6 Measurement traceability 

 5.6.1 General 

____ a) All equipment used for tests and/or calibrations, including equipment for subsidiary 

measurements (e.g., for environmental conditions) having a significant effect on the accuracy 

or validity of the result of the test, calibration or sampling shall be calibrated before being 

put into service. 

 

____ b) The laboratory shall have an established program and procedure for the calibration of its 

equipment. 

NOTE Such a program should include a system for selecting, using, calibrating, checking, 

controlling and maintaining measurement standards, reference materials used as measurement 

standards, and measuring and test equipment used to perform tests and calibrations. 

 5.6.2 Specific requirements 

 5.6.2.1 Calibration 

 5.6.2.1.1 

____ a) For calibration laboratories, the program for calibration of equipment shall be designed and 

operated so as to ensure that calibrations and measurements made by the laboratory are 

traceable to the International System of Units (SI) (Système international d'unités). 

 

 A calibration laboratory establishes traceability of its own measurement standards and 

measuring instruments to the SI by means of an unbroken chain of calibrations or 

comparisons linking them to relevant primary standards of the SI units of measurement. The 

link to SI units may be achieved by reference to national measurement standards. National 

measurement standards may be primary standards, which are primary realizations of the SI 

units or agreed representations of SI units based on fundamental physical constants, or they 

may be secondary standards which are standards calibrated by another national metrology 

institute. 

____ b) When using external calibration services, traceability of measurement shall be assured by the 
NIST Handbook 143 117 March 2003

use of calibration services from laboratories that can demonstrate competence, measurement 

capability and traceability. 

 

____ c) The calibration certificates issued by these laboratories shall contain the measurement 

results, including the measurement uncertainty and/or a statement of compliance with an 

identified metrological specification (see also 5.10.4.2). 

NOTE 1 Calibration laboratories fulfilling the requirements of this Handbook are considered to be 

competent. A calibration certificate bearing an accreditation body logo from a calibration laboratory 

accredited to this Handbook, for the calibration concerned, is sufficient evidence of traceability of the 

calibration data reported. 

 NOTE 2 Traceability to SI units of measurement may be achieved by reference to an appropriate 

primary standard (see VIM:1993, 6.4) or by reference to a natural constant, the value of which in 

terms of the relevant SI unit is known and recommended by the General Conference of Weights and 

Measures (CGPM) and the International Committee for Weights and Measures (CIPM). 

 NOTE 3 Calibration laboratories that maintain their own primary standard or representation of SI 

units based on fundamental physical constants can claim traceability to the SI system only after these 

standards have been compared, directly or indirectly, with other similar standards of a national 

metrology institute. 

 NOTE 4 The term "identified metrological specification" means that it must be clear from the 

calibration certificate which specification the measurements have been compared with, by including 

the specification or by giving an unambiguous reference to the specification. 

 NOTE 5 When the terms "international standard" or "national standard" are used in connection with 

traceability, it is assumed that these standards fulfill the properties of primary standards for the 

realization of SI units. 

 NOTE 6 Traceability to national measurement standards does not necessarily require the use of the 

national metrology institute of the country in which the laboratory is located. 

 NOTE 7 If a calibration laboratory wishes or needs to obtain traceability from a national metrology 

institute other than in its own country, this laboratory should select a national metrology institute that 

actively participates in the activities of BIPM either directly or through regional groups. 

 NOTE 8 The unbroken chain of calibrations or comparisons may be achieved in several steps 

carried out by different laboratories that can demonstrate traceability. 

____ 5.6.2.1.2 There are certain calibrations that currently cannot be strictly made in SI units. In these 

cases calibration shall provide confidence in measurements by establishing traceability 

to appropriate measurement standards such as: 

 

____ a) the use of certified reference materials provided by a competent supplier to give a reliable 

physical or chemical characterization of a material; 

 

____ b) the use of specified methods and/or consensus standards that are clearly described and agreed 

by all parties concerned. 

 

____ c) Participation in a suitable program of interlaboratory comparisons is required where possible.

 5.6.2.2 Testing 
NIST Handbook 143 118 March 2003

___F 5.6.2.2.1 For testing laboratories, the requirements given in 5.6.2.1 apply for measuring and test 

equipment with measuring functions used, unless it has been established that the 

associated contribution from the calibration contributes little to the total uncertainty of 

the test result. When this situation arises, the laboratory shall ensure that the equipment 

used can provide the uncertainty of measurement needed. 

NOTE The extent to which the requirements in 5.6.2.1 should be followed depends on the relative 

contribution of the calibration uncertainty to the total uncertainty. If calibration is the dominant 

factor, the requirements should be strictly followed. 

 

___F 5.6.2.2.2 Where traceability of measurements to SI units is not possible and/or not relevant, the 

same requirements for traceability to, for example, certified reference materials, agreed 

methods and/or consensus standards, are required as for calibration laboratories (see 

5.6.2.1.2). 

 5.6.3 Reference standards and reference materials 

 5.6.3.1 Reference standards 

____ a) The laboratory shall have a program and procedure for the calibration of its reference 

standards. 

 

____ b) Reference standards shall be calibrated by a body that can provide traceability as described 

in 5.6.2.1. 

 

____ c) Such reference standards of measurement held by the laboratory shall be used for calibration 

only and for no other purpose, unless it can be shown that their performance as reference 

standards would not be invalidated. Reference standards shall be calibrated before and after 

any adjustment. 

 5.6.3.2 Reference materials 

____ Reference materials shall, where possible, be traceable to SI units of measurement, or to certified 

reference materials. Internal reference materials shall be checked as far as is technically and 

economically practicable. 

 5.6.3.3 Intermediate checks 

____ Checks needed to maintain confidence in the calibration status of reference, primary, transfer or 

working standards and reference materials shall be carried out according to defined procedures and 

schedules 
NIST Handbook 143 119 March 2003

 5.6.3.4 Transport and storage 

___F The laboratory shall have procedures for safe handling, transport, storage and use of reference 

standards and reference materials in order to prevent contamination or deterioration and in order to 

protect their integrity. 

 

NOTE Additional procedures may be necessary when reference standards and reference materials 

are used outside the permanent laboratory for tests, calibrations or sampling. 

5.7 Sampling 

 5.7.1 

____ a) The laboratory shall have a sampling plan and procedures for sampling when it carries out 

sampling of substances, materials or products for subsequent testing or calibration. 

 

___F b) The sampling plan as well as the sampling procedure shall be available at the location where 

sampling is undertaken. Sampling plans shall, whenever reasonable, be based on appropriate 

statistical methods. The sampling process shall address the factors to be controlled to ensure 

the validity of the test and calibration results. 

 NOTE 1 Sampling is a defined procedure whereby a part of a substance, material or product is taken 

to provide for testing or calibration of a representative sample of the whole. Sampling may also be 

required by the appropriate specification for which the substance, material or product is to be tested 

or calibrated. In certain cases (e.g., forensic analysis), the sample may not be representative but is 

determined by availability. 

 NOTE 2 Sampling procedures should describe the selection, sampling plan, withdrawal and 

preparation of a sample or samples from a substance, material or product to yield the required 

information. 

___F 5.7.2 Where the client requires deviations, additions or exclusions from the documented sampling 

procedure, these shall be recorded in detail with the appropriate sampling data and shall be 

included in all documents containing test and/or calibration results, and shall be 

communicated to the appropriate personnel. 

 

___F 5.7.3 The laboratory shall have procedures for recording relevant data and operations relating to 

sampling that forms part of the testing or calibration that is undertaken. These records shall 

include the sampling procedure used, the identification of the sampler, environmental 

conditions (if relevant) and diagrams or other equivalent means to identify the sampling 

location as necessary and, if appropriate, the statistics the sampling procedures are based 

upon. 

5.8 Handling of test and calibration items 

____ 5.8.1 The laboratory shall have procedures for the transportation, receipt, handling, protection, 

storage, retention and/or disposal of test and/or calibration items, including all provisions 

necessary to protect the integrity of the test or calibration item, and to protect the interests of 

the laboratory and the client. 
NIST Handbook 143 120 March 2003

 5.8.2 

____ a) The laboratory shall have a system for identifying test and/or calibration items. 

 

___F b) The identification shall be retained throughout the life of the item in the laboratory. 

 

____ c) The system shall be designed and operated so as to ensure that items cannot be confused 

physically or when referred to in records or other documents. 

 

___F d) The system shall, if appropriate, accommodate a sub-division of groups of items and the 

transfer of items within and from the laboratory. 

 5.8.3 

____ a) Upon receipt of the test or calibration item, abnormalities or departures from normal or 

specified conditions, as described in the test or calibration method, shall be recorded. 

 

____ b) When there is doubt as to the suitability of an item for test or calibration, or when an item 

does not conform to the description provided, or the test or calibration required is not 

specified in sufficient detail, the laboratory shall consult the client for further instructions 

before proceeding and shall record the discussion. 

 5.8.4 

____ a) The laboratory shall have procedures and appropriate facilities for avoiding deterioration, 

loss or damage to the test or calibration item during storage, handling and preparation. 

 

____ b) Handling instructions provided with the item shall be followed. 

 

____ c) When items have to be stored or conditioned under specified environmental conditions, these 

conditions shall be maintained, monitored and recorded. 

 

____ d) Where a test or calibration item or a portion of an item is to be held secure, the laboratory 

shall have arrangements for storage and security that protect the condition and integrity of 

the secured items or portions concerned. 

NOTE 1 Where test items are to be returned into service after testing, special care is required to 

ensure that they are not damaged or injured during the handling, testing or storing/waiting processes.

 NOTE 2 A sampling procedure and information on storage and transport of samples, including 

information on sampling factors influencing the test or calibration result, should be provided to those 

responsible for taking and transporting the samples. 

 NOTE 3 Reasons for keeping a test or calibration item secure can be for reasons of record, safety or 

value, or to enable complementary tests and/or calibrations to be performed later. 

5.9 Assuring the quality of test and calibration results 

____ a) The laboratory shall have quality control procedures for monitoring the validity of tests and 

calibrations undertaken. 

 

____ b) The resulting data shall be recorded in such a way that trends are detectable and, where 
NIST Handbook 143 121 March 2003

practicable, statistical techniques shall be applied to the reviewing of the results. 

 

____ c) This monitoring shall be planned and reviewed and may include, but not be limited to, the 

following: 

 ____ 1) regular use of certified reference materials and/or internal quality control using 

secondary reference materials; 

 

 ____ 2) participation in interlaboratory comparison or proficiency-testing programs; 

 

 ____ 3) replicate tests or calibrations using the same or different methods; 

 

 ____ 4) retesting or recalibration of retained items; 

 

 ____ 5) correlation of results for different characteristics of an item. 

 

NOTE The selected methods should be appropriate for the type and volume of the work 

undertaken. 

5.10 Reporting the results 

 5.10.1 General 

____ a) The results of each test, calibration, or series of tests or calibrations carried out by the 

laboratory shall be reported accurately, clearly, unambiguously and objectively, and in 

accordance with any specific instructions in the test or calibration methods. 

 

____ b) The results shall be reported, usually in a test report or a calibration certificate (see note 1), 

and shall include all the information requested by the client and necessary for the 

interpretation of the test or calibration results and all information required by the method 

used. This information is normally that required by 5.10.2, and 5.10.3 or 5.10.4. 

 

____ c) In the case of tests or calibrations performed for internal clients, or in the case of a written 

agreement with the client, the results may be reported in a simplified way. Any 

information listed in 5.10.2 to 5.10.4 which is not reported to the client shall be readily 

available in the laboratory which carried out the tests and/or calibrations. 

 NOTE 1 Test reports and calibration certificates are sometimes called test certificates and 

calibration reports, respectively. 

 

 NOTE 2 The test reports or calibration certificates may be issued as hard copy or by electronic data 

transfer provided that the requirements of this Handbook are met. 

 5.10.2 Test reports and calibration certificates 

Each test report or calibration certificate shall include at least the following information, unless the 

laboratory has valid reasons for not doing so: 

____ a) a title (e.g., "Test Report" or "Calibration Certificate"); 

 

____ b) the name and address of the laboratory, and the location where the tests and/or calibrations 

were carried out, if different from the address of the laboratory; 

____ c) unique identification of the test report or calibration certificate (such as the serial number), 
NIST Handbook 143 122 March 2003

and on each page an identification in order to ensure that the page is recognized as a part of 

the test report or calibration certificate, and a clear identification of the end of the test report 

or calibration certificate; 

____ d) the name and address of the client; 

 

____ e) identification of the method used; 

 

____ f) a description of, the condition of, and unambiguous identification of the item(s) tested or 

calibrated; 

____ g) the date of receipt of the test or calibration item(s) where this is critical to the validity and 

application of the results, and the date(s) of performance of the test or calibration; 

____ h) reference to the sampling plan and procedures used by the laboratory or other bodies where 

these are relevant to the validity or application of the results; 

 

____ i) the test or calibration results with, where appropriate, the units of measurement; 

 

____ j) the name(s), function(s) and signature(s) or equivalent identification of person(s) authorizing 

the test report or calibration certificate; 

 

____ k) where relevant, a statement to the effect that the results relate only to the items tested or 

calibrated. 

 WMD Note: WMD defines the person(s) who authorizes the test report or calibration certificate as 

the Approved Signatory. 

 

 NOTE 1 Hard copies of test reports and calibration certificates should also include the page number 

and total number of pages. 

 

NOTE 2 It is recommended that laboratories include a statement specifying that the test report or 

calibration certificate shall not be reproduced except in full, without written approval of the 

laboratory. 

 5.10.3 Test reports 

 5.10.3.1 In addition to the requirements listed in 5.10.2, test reports shall, where necessary for 

the interpretation of the test results, include the following: 

____ a) deviations from, additions to, or exclusions from the test method, and information on specific 

test conditions, such as environmental conditions; 

 

___F b) where relevant, a statement of compliance/non-compliance with requirements and/or 

specifications; 

 

____ c) where applicable, a statement on the estimated uncertainty of measurement; information on 

uncertainty is needed in test reports when it is relevant to the validity or application of the 

test results, when a client's instruction so requires, or when the uncertainty affects 

compliance to a specification limit; 

 

___F d) where appropriate and needed, opinions and interpretations (see 5.10.5); 

 

___F e) additional information which may be required by specific methods, clients or groups of 
NIST Handbook 143 123 March 2003

clients. 

 5.10.3.2 In addition to the requirements listed in 5.10.2 and 5.10.3.1, test reports containing the 

results of sampling shall include the following, where necessary for the interpretation of 

test results: 

___F a) the date of sampling; 

___F b) unambiguous identification of the substance, material or product sampled (including the 

name of the manufacturer, the model or type of designation and serial numbers as 

appropriate); 

___F c) the location of sampling, including any diagrams, sketches or photographs; 

 

___F d) a reference to the sampling plan and procedures used; 

___F e) details of any environmental conditions during sampling that may affect the interpretation of 

the test results; 

 

___F f) any standard or other specification for the sampling method or procedure, and deviations, 

additions to or exclusions from the specification concerned. 

 5.10.4 Calibration certificates 

 5.10.4.1 In addition to the requirements listed in 5.10.2, calibration certificates shall include the 

following, where necessary for the interpretation of calibration results: 

____ a) the conditions (e.g., environmental) under which the calibrations were made that have an 

influence on the measurement results; 

 

____ b) the uncertainty of measurement and/or a statement of compliance with an identified 

metrological specification or clauses thereof; 

 

____ c) evidence that the measurements are traceable (see note 2 in 5.6.2.1.1). 

 5.10.4.2 

____ a) The calibration certificate shall relate only to quantities and the results of functional tests. 

 

___F b) If a statement of compliance with a specification is made, this shall identify which clauses of 

the specification are met or not met. 

 

___F c) When a statement of compliance with a specification is made omitting the measurement 

results and associated uncertainties, the laboratory shall record those results and maintain 

them for possible future reference. 

 

___F d) When statements of compliance are made, the uncertainty of measurement shall be taken into 

account. 

___F 5.10.4.3 When an instrument for calibration has been adjusted or repaired, the calibration results 

before and after adjustment or repair, if available, shall be reported. 

 
NIST Handbook 143 124 March 2003

___F 5.10.4.4 A calibration certificate (or calibration label) shall not contain any recommendation on 

the calibration interval except where this has been agreed with the client. This 

requirement may be superseded by legal regulations. 

 5.10.5 Opinions and interpretations 

___F When opinions and interpretations are included, the laboratory shall document the basis upon which 

the opinions and interpretations have been made. Opinions and interpretations shall be clearly 

marked as such in a test report. 

 

 NOTE 1 Opinions and interpretations should not be confused with inspections and product 

certifications as intended in ISO/IEC 17020 and ISO/IEC Guide 65. 

 

 NOTE 2 Opinions and interpretations included in a test report may comprise, but not be limited to, 

the following: 

• an opinion on the statement of compliance/noncompliance of the results with requirements;

 

• fulfillment of contractual requirements; 

 

• recommendations on how to use the results; 

 

• guidance to be used for improvements. 

 NOTE 3 In many cases it might be appropriate to communicate the opinions and interpretations by 

direct dialogue with the client. Such dialogue should be written down. 

 5.10.6 Testing and calibration results obtained from subcontractors 

____ a) When the test report contains results of tests performed by subcontractors, these results shall 

be clearly identified. 

 

___F b) The subcontractor shall report the results in writing or electronically. 

 

___F c) When a calibration has been subcontracted, the laboratory performing the work shall issue 

the calibration certificate to the contracting laboratory. 

 5.10.7 Electronic transmission of results 

____ In the case of transmission of test or calibration results by telephone, telex, facsimile or other 

electronic or electromagnetic means, the requirements of this Handbook shall be met (see also 5.4.7).

 5.10.8 Format of reports and certificates 

____ The format shall be designed to accommodate each type of test or calibration carried out and to 

minimize the possibility of misunderstanding or misuse. 

 

 NOTE 1 Attention should be given to the layout of the test report or calibration certificate, 

especially with regard to the presentation of the test or calibration data and ease of assimilation by 

the reader. 

 

NOTE 2 The headings should be standardized as far as possible. 
NIST Handbook 143 125 March 2003

 

 5.10.9 Amendments to test reports and calibration certificates 

 

____ a) Material amendments to a test report or calibration certificate after issue shall be made only 

in the form of a further document, or data transfer, which includes the statement: 

 "Supplement to Test Report [or Calibration Certificate], serial number ... [or as 

otherwise identified]," or an equivalent form of wording. 

 

____ b) Such amendments shall meet all the requirements of this Handbook. 

____ c) When it is necessary to issue a complete new test report or calibration certificate, this shall 

be uniquely identified and shall contain a reference to the original that it replaces. 
NIST Handbook 143 126 March 2003

Appendix D. Summary of Services for Laboratory Directory

 State 

 Recognition Period: __________ 

Laboratory Staff & Titles Address Communications 

 Phone: 

 Fax: 

e-mail: 

URL: 

Services Available

Parameter Range Uncertainty* 

Mass, I 

Mass, II 

Mass, III 

Length, Tapes - Bench 

Length, Tapes - Tape 

Length, Rigid Rules 

Volume, Gravimetric 

Volume, Transfer 

Temperature, I 

Temperature, II 

Temperature, III 

Temperature, IV 

Temperature, V 

Tuning Forks 

Hydrometers 

Time 

Moisture 

* Uncertainties Chart must be completed for each measurement parameter listed.
NIST Handbook 143 127 March 2003

 State

Fees 

National Type Evaluation Program (NTEP) 

Address Telephone Number 

 

Commercial Measuring Device Testing (non-NTEP) 

Address Telephone Number 

 
 NIST Handbook 143 129 March 2003

 State

Grain Moisture Testing 

Address Telephone Number 

 

Petroleum Quality Testing 

Address Telephone Number 

 

 

 
NIST Handbook 143 130 March 2003

Appendix E. Uncertainties Chart for Measurement Parameter_____________________

Laboratory___________________________ 

Range Type A Uncertainty Type B Uncertainty Combined Uncertainty Expanded Standard Uncertainty (k = 2 or 3) Com