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NDT Certification System

The need for competent personnel to perform NDT tasks is paramount in all industries. In order to determine competency, systems have been devised to ensure that NDT personnel have the proper training, have passed written and practical examinations, and have enough experience to properly perform NDT tasks using the applicable test method or technique. Personnel that have met all three of these requirements are said to be “qualified,” and once qualified they can be certified, which is defined in several different ways under the various NDT systems.

The following terms are used here for descriptive purposes only and should not be considered to be formal (or “official”) definitions:

    Certification Standard: National or international documents describing the requirements for the qualification and certification of NDT personnel. (See the Codes and Standards web page.

    Recommended Practice: A formal document that provides nationally or internationally recognized guidelines, and describes the qualification and certification process for NDT personnel. If mandated by governing codes, standards, specifications or contract documents, these guidelines become requirements for the specified project.

    Certification System: The combination of the standard or recommended practice governing the certification requirements, the third-party certification program (if applicable) or the employer's written practice, and additional employer documents used in the administration of their certification program.

    Certification Program: The documented employer’s or certification body’s procedures and processes based on a standard or recommended practice, which defines the requirements of that specific program.


NDT Certification Systems

There are multiple NDT certification systems worldwide, but they can generally be divided into two main types: “employer-based” and “central” certification systems.

Employer-based certification systems are systems in which the employers are responsible for the administration of the training and the qualification examinations of their own employees, as well as the documentation of the required training, examinations and experience in accordance with an employer-based standard or recommended practice. Most employer-based systems do allow the employer to accept training and examination services provided by outside agencies provided it is properly documented and the employer has determined that the content of those services meet their own company requirements as described in the employer's Written Practice.

Upon proof of qualification, the employer may issue a certificate, which can be a formal certificate or in letter format, and can authorize their personnel to perform NDT tasks. In all employer-based systems, the employer is responsible for authorizing their personnel to perform such work. Because employer-based certification is usually tailored to an employer's specific needs, the resulting certifications expire when an employee leaves the company that issued the certification.

Central certification systems are systems in which the qualification examinations are administered by an independent third-party certification body based on a central certification standard. To be eligible to sit for these examinations, prospective candidates must provide acceptable documentation of their training and experience to the certification body. Upon successful completion of the third-party examinations, the certification body will issue a certificate attesting to the fact that the named certificate holder has met the requirements and passed the examinations described in the third-party certification system. The employer can then choose to accept the third-party certificate(s) as proof of qualification. As with employer-based systems, the employer has the ultimate responsibility to certify (authorize) the certificate holder to perform NDT tasks.

Levels of Qualification

Most certification programs have three levels of NDT qualification: Level I, Level II and Level III. Because the requirements for the levels are very similar, the descriptions provided here are from the 2006 edition of the ASNT Recommended Practice No. SNT-TC-1A.

  • An NDT Level I individual should be qualified to properly perform specific calibrations, specific NDT and specific evaluations for acceptance or rejection determinations according to written instructions and to record results. The NDT Level I should receive the necessary instruction and supervision from a certified NDT Level II or III individual.
  • An NDT Level II individual should be qualified to set up and calibrate equipment and to interpret and evaluate results with respect to applicable codes, standards and specifications. The NDT Level II should be thoroughly familiar with the scope and limitations of the methods for which they are qualified and should exercise assigned responsibility for on-the-job training and guidance of trainees and NDT Level I personnel. The NDT Level II should be able to organize and report the results of NDT tests.
  • An NDT Level III individual should be capable of developing, qualifying and approving procedures, establishing and approving techniques, interpreting codes, standards, specifications and procedures, as well as designating the particular NDT methods, techniques and procedures to be used. The NDT Level III should be responsible for the NDT operations for which they are qualified and assigned and should be capable of interpreting and evaluating results in terms of existing codes, standards and specifications. The NDT Level III should have sufficient practical background in applicable materials, fabrication and product technology to establish techniques and to assist in establishing acceptance criteria when none are otherwise available. The NDT Level III should have general familiarity with other appropriate NDT methods, as demonstrated by an ASNT Level III Basic examination or other means. The NDT Level III, in the methods in which they are certified, should be capable of training and examining NDT Level I and II personnel for certification in those methods.
  • Trainee: Though not a certification level, a trainee is a person who is in the process of being initially trained, qualified and certified, and should work with a certified individual. A trainee may not independently conduct, interpret, evaluate or report the results of any NDT test.
  • NDT Instructor: The term “NDT Instructor” is used in the ANSI/ASNT standard CP-189, ASNT Standard for Qualification and Certification of Nondestructive Testing Personnel, to describe an individual with the skills and knowledge to plan, organize and present classroom, laboratory, demonstration, and/or on-the-job NDT instruction, training and/or education programs.


Core Certification Requirements: Training, Examination, Experience

Training. NDT training is based on Topical (Training Course) Outlines. The collection of these outlines form a document called the NDT Body of Knowledge (BOK). The development of the BOK starts with subject-matter experts from industry who performing a Job Task Analysis (JTA), which determines what knowledge and skills are required for the different levels of qualification. The second step is to determine what training topics are necessary to adequately cover the knowledge requirements for each level of qualification as defined by the JTA. Finally, reference materials must be identified so that personnel striving for certification can study the required subject matter prior to taking the qualification examinations.

The ASNT NDT Body of Knowledge can be found in the ANSI/ASNT American National Standard CP-105, ASNT Standard Topical Outlines for Qualification of Nondestructive Testing Personnel.

Written Examinations. Two written examinations are used in the qualification of Level Is and IIs, a general and a specific examination. The general examination should address the fundamentals, principles and theory of the applicable test method. The specific examination should address the equipment, operating procedures and NDT techniques that the individual may encounter during specific assignments; it should also cover the specifications or codes and acceptance criteria to be used in the anticipated NDT tasks. The number of questions required for each examination is described in the applicable certification standard or recommended practice.

For employer-administered examinations, an NDT Level III should develop examination content so that it addresses the test methods, techniques, codes and specifications that the candidate may encounter during specific assignments. For central certification programs, ISO 17024 requires that examinations are fair, valid and reliable. Appropriate methodology and procedures (such as collecting and maintaining statistical data) are required to reaffirm the fairness, validity, reliability and general performance of each examination and to correct all identified deficiencies on an annual basis.

Practical Examination. The practical examination should require that the candidate demonstrate familiarity with, and the ability to operate, the necessary NDT equipment and to record and analyze the resultant information to the degree required. At least ten (10) different checkpoints requiring an understanding of test variables and the employer’s procedural requirements should be included in this practical examination.

Due to the fact that central certification program examinations cannot cover all phases of all test methods and techniques, employers – who have the ultimate responsibility for authorizing personnel to perform NDT tasks – must determine if the central certification examinations meet their needs. If not, additional job-specific employer examinations may be required.

NOTE: Under employer-based certification systems, only the employer can certify (authorize) NDT personnel to perform NDT tasks. Providers of outside training and examination services may issue certificates of completion identifying the training and examinations that were successfully completed, but this does NOT constitute NDT certification. Employers must document in their Written Practice that they will accept such training and examinations, then after documenting the individual's experience and current visual acuity test, the employer may certify the individual to perform NDT work.

Experience. Experience is defined in SNT-TC-1A as, “work activities accomplished in a specific NDT method under the direction of qualified supervision including the performance of the NDT method and related activities but not including time spent in organized training programs.” Other certification documents have similar definitions. The amount of experience-time required for each test method and/or technique varies depending upon the complexity of the inspection process and the difficulty in interpreting test results.

Every certification document has differing requirements, though they are generally similar in nature. The table and supplemental notes shown below give a comparison of the training and experience requirements for the following:

ANSI/ASNT CP-105, Nondestructive Testing - Qualification and Certification of Personnel;
Recommended Practice No. SNT-TC-1A, Personnel Qualification and Certification in Nondestructive Testing;
ASNT Central Certification Program (ACCP) Document ACCP-CP-1, Rev. 6 (8/9/09);
ISO 9712, Non-destructive testing - Qualification and certification of personnel; and
EN 473, Non-destructive testing - Qualification and certification of NDT personnel - General principles.

More information on the above standards and Recommended Practice can be found on the Codes and Standards Bodies web page.


a    The training and experience hours for the U.S. adoption of ISO 9712, CP-106, and Recommended Practice No SNT-TC-1A:2006 are the same. SNT-TC-1A recommends initial training hours; all other documents just list minimum training hours.
b    CP-106 and Recommended Practice No. SNT-TC-1A do not require additional training to Level III.
c    Practical training may be used for up to 50% of the training hours in these Methods.
d    CP-106, SNT-TC-1A and the ACCP require time in grade as a Level II based on the person's level of formal education.
e    Times are additive; i.e., for UT Level III, total training time is 160 (40+80+40) and experience times = 3+9+18, or 30 months total.
f     If the individual is being qualified directly to level 3, with no time at level 2, the experience shall consist of the sum of the times required for level 2 and level 3. With Tech School degree or 2+ years of Engineering or Science study at an accredited college; without these qualifications, the months of required experience time is doubled.
g     ET training and experience times in SNT-TC-1A are per Technique, and are by Method in CP-106 and the ACCP.
h     ISO 9712:2005 supplemental Training notes:
1     Training hours are based upon candidates possessing basic mathematical skills and prior knowledge of materials and processes. If this is not the case, additional training may be required by the certification body.
2     Training hours include both practical and theory courses.
3     Training duration may be reduced by up to 50% when the certification sought is limited in application of the method.
4     A reduction of up to 50% in the total required number of training hours may be accepted by the certification body for candidates who have graduated from technical college or university, or have completed at least two years of engineering or science study at college or university.

i    EN 473:2008 supplemental Training notes:
1   Direct access to level 2 examination requires the total hours shown for level 1 and level 2.
2   Training duration may be reduced by up to 50% when the certification sought is limited: 
      - in application (e.g. automated ET, MT, UT of bar, tube and rod, or normal beam ultrasonic thickness and lamination testing of rolled steel plate); 
     - in technique (e.g. RT using only Radioscopy); 
     - for RT and UT, level 1, in only one product sector.
3     Training duration may be reduced by up to 50% when the candidate is a certified level 2 in the method.
4     Up to 50% of the required training duration may be acquired by practical training agreed by the certification body.
5     A reduction of up to 50% in the total required number of training hours may be accepted by the Certification Body for candidates who have graduated from technical college or university, or have completed at least two years of engineering or science study at college or university.
6     When certification is restricted to the film interpretation and to only one product sector, a minimum training requirement of 56 h applies for direct access. Footnote “a” is not applicable.
7     Maximum reduction may be 50%.

Other Components of an Employer-Based Certification Program

In addition to training, examinations and experience, there are multiple other requirements for the development and administration of an in-house certification program, including development of a Written Practice (or procedure), recertification requirements and certification documentation.

Written Practice. Because Recommended Practice No. SNT-TC-1A provides guidelines; employers are required to create a company NDT certification procedure known as a “Written Practice.” Employers must review the SNT-TC-1A guidelines and determine which guidelines apply to their NDT requirements, then they must create a procedure for the control and administration of NDT personnel training, examination and certification. The Written Practice should describe the responsibility of each level of certification for determining the acceptability of materials or components in accordance with applicable codes, standards, specifications and procedures, and must describe the training, experience and examination requirements for each level of certification. When included in the Written Practice, the selected guidelines become the certification requirements for the company.

Because paragraph 1.4 of SNT-TC-1A permits employers to modify the guidelines to meet their particular needs, the recurring question regarding Written Practice can be modified. This question was submitted to the ASNT SNT-TC-1A Interpretation Panel as the first formal Inquiry of 2004 ("04-1"), and that inquiry and the Panel's official response are shown below. This Inquiry (and all others from 1975 through 2009) can be found in the ASNT publication Interpreting SNT-TC-1A, which is available to ASNT members as a PDF download in the Members Only portion of the ASNT website, and is available for purchase through the ASNT online bookstore, ShopASNT. The Catalog ("Item") number is 2040.

Inquiry 04-1

  1. Is it the intent of Paragraph 1.4 that an employer can modify the “Guidelines” of SNT-TC-1A to the extent that Level II and Level III NDT personnel can be “certified” without any examinations if written this way in the written practice?
  2. What are the limits that are intended regarding how much the employer can deviate from SNT-TC-1A as written? If no limits are given, the employer can change the entire context of SNT-TC-1A to eliminate all certification exams. Is that the intent?



  1. No. The provisions of Paragraph 1.4 allow modification of the detailed recommendations; it is not intended to allow elimination of the basic provisions of the document.
  2. No. Paragraph 9.2 requires certification in accordance with “Section 8, Examinations” as described in the employer’s written practice.


General Comments:

SNT-TC-1A allows for modification of detailed recommendations as necessary to meet particular needs. The intent is for a technical rationale to be present to support such modification. Elimination of requirements, such as training, experience and examination, goes beyond modification of detailed requirements.

Although CP-189, NAS 410 and EN 4179 are standards with requirements rather than guidelines, all three documents require employers to establish a Written Practice describing the process used to train, qualify and certify their NDT personnel.

Recertification. All NDT certification programs require that certified personnel renew or recertify their certifications at regular intervals. The 2006 edition of Recommended Practice No. SNT-TC-1A recommends that all levels of qualification renew at five-year intervals, which can be done by showing evidence of continuing satisfactory technical performance or by re-examination in those portions of the initial certification examinations deemed necessary by the employer’s NDT Level III. The renewal/recertification process is to be documented in the certified person’s company certification file regardless of the renewal method.

CP-189:2006 states that an individual may be recertified if the individual has at least two months (350 hours) of documented experience using the applicable method over the five-year certification interval and has successfully passed a specific examination that complies with the initial certification requirements. At least every ten years, the individual must repeat the initial certification examinations.

Revision 3 of NAS 410 (3/08) has the following recertification requirements:

  • Level I-limited personnel shall be re-certified at intervals not to exceed one year for each certification held;
  • Levels II and III personnel must recertify at intervals not to exceed five years and must successfully complete practical and specific examinations equivalent to those required for initial certification.
  • Level III personnel must recertify at intervals not to exceed five years. Recertification may be done by submitting documentation of having earned 24 recertification points as described in Appendix A, Table A.1, or by successful completion of specific and practical examinations equivalent to initial certification. If equipment operation or accepting hardware is required as a part of the Level III’s duties, an additional hands-on practical examination equivalent to Level II is required.


Documentation. All employer-based NDT certification programs require that the employer maintain a certification file for all personnel holding NDT certifications. CP-189 specifies additional documentation requirements that include as a minimum: a training record, a certification record, an experience record, a record of previous experience (if applicable), employee’s current examinations, and a vision examination record. The documentation requirements for SNT-TC-1A, CP-189 and NAS 410 are shown in the table below. (EN 4179 has requirements identical to those shown for NAS 410.)

Documentation Requirements


SNT-TC-1A   CP-189   NAS 410 / EN 4179  

Name of certified individual.
Level of certification and NDT method.
Educational background and experience of certified individuals.
Statement indicating satisfactory completion of training in accordance with the employer’s Written Practice.
Results of the vision examinations for the current certification period.
Current examination copies or evidence of successful completion of examinations.
Other suitable evidence of satisfactory qualifications when such qualifications are used in lieu of the specific examination or as described in the employer’s Written Practice.
Composite grade(s) or suitable evidence of grades.
Signature of the Level III that verified qualifications of candidate for certification.
Dates of certification and/or recertification and the dates of assignments to NDT.
Certification expiration date. Signature of employer’s certifying authority.

Certification Record.
The certification record shall include at least the following information:
Level of certification and NDT method, including the test technique(s) covered; results of current employer examinations that the individual has taken;
for Level III personnel, a copy of the candidate’s ASNT Level III certificate;
dates of certification, expiration, suspension, revocation and reinstatement;
and the signature, printed name, and title of the employer’s certifying authority.

NDT Training Record.
A documented history of the employee’s training shall be maintained, which identifies:
NDT training received by the individual;
the organization providing the training;
dates of the training;
hours of training;
evidence of satisfactory completion;
and the instructor’s name.

NDT Experience Record.
A record that identifies the individual’s experience performing various nondestructive tests must be maintained for purposes of verifying initial certification experience and continuing experience.

Record of Previous Experience.
Documented evidence of the individual’s previous NDT training and experience must be maintained if previous training and experience are used to satisfy any part of the requirements of this standard.

Visual Examination Records. Current records of vision examinations required by 6.1 must be maintained.

Name of the certified individual. Level, method, and technique(s) for which individual is certified.
The latest written and practical examinations and the scores from the immediately previous exams.
If Annex A is used, documentation of credit points used for Level III recertification.
Date and expiration of current certification(s).
NDT training history that identifies the source, type of training, dates of training and course hours, and, if applicable, the documentation required by paragraphs 6.1.2 and 6.1.3.
NDT experience history, including any previous certifications, both with current and previous employers sufficient to justify satisfaction of experience requirements for qualification, and, if applicable, the documentation required by paragraphs 6.3.1 and 6.3.2. Results of the most-recent (i.e. current) visual acuity and color perception examinations. Extent and documentation of formal education when used to meet qualification requirements.
The name and signature of the employer’s representative authorizing the certification.
For Level I-limited certifications, the case-by-case justification, the cognizant engineering organization’s approval, the training and experience hours, the length of the certification (up to one year), the specific NDT test to be performed, the specific hardware to be tested, and, if applicable, the approval to accept or reject hardware.

Use of Central Certification Documentation for Employer-Based Programs

Many countries have their own technical industry standards, and many of these only reference NDT certification standards from their own country. As a result, certifications from the various central certification programs may not be accepted as meeting the requirements of the governing codes, standards or specifications for a given project. This is not an uncommon circumstance when a governing document references out to Recommended Practice No. SNT-TC-1A for NDT certification.

In such cases, the NDT service provider may be required to create an in-house, employer-based certification program in order to meet those requirements. To do this with minimal effort, service suppliers should consider the fact that training and experience do not expire, provided they are properly documented. If the company’s Written Practice (required by SNT-TC-1A) addresses the acceptance of both in-house and third-party training and examinations, and the central certification training and examination requirements meet or exceed the SNT-TC-1A guidelines, then the employer can use the outside training and examinations to satisfy the guidelines of SNT-TC-1A.

Employers using this method may wish to develop a comparison table like the one shown above so that it can be shown to auditors should they question the dual use of the same documentation. Employers may also wish to keep copies of the training and examination documentation provided to certified individuals by the central certification body onsite in the event that an auditor might ask for them. In some cases, auditors may not accept a third-party NDT certificate and ask to see the actual examination results (or results letter) and training records; the need to send copies from the certification body can result in a finding by the auditor. (It should also be noted that SNT-TC-1A requires that the employer have examination copies or evidence of successful completion of examinations and training documentation in each individual’s certification record.)