How to Become an NDT Level I, II or III

Start with the three levels

The levels describe what a person is trusted to do. Most schemes follow the same broad pattern, with two spelling differences that matter: SNT-TC-1A and CP-189 write Level I, II and III, while NAS410 writes Level 1, 2 and 3. Seeing the numerals is often the quickest way to tell which scheme a certificate belongs to.

• Trainee. Someone learning the method. A trainee works alongside certified people, does not work independently and does not make accept or reject decisions.
• Level I. Follows written instructions: carries out specific tests and calibrations and records the results, with guidance from a Level II or III. Whether a Level I may accept or reject product depends on the written practice.
• Level II. Sets up and standardizes equipment, interprets and evaluates results against the applicable code or specification, reports them, and guides trainees and Level I staff.
• Level III. Carries technical responsibility: selecting methods and techniques, interpreting codes, writing or approving procedures, and training and examining other people. NAS410 also has a Level 1-Limited, and employers may subdivide levels under either scheme.

Certification is per method. A UT Level II is not a PT Level II, and a Level III in one method has no standing as a Level III in another.

Employer-based or central certification

This is the biggest difference between schemes, and it decides who stands behind the certificate.

Employer-based certification means your employer certifies you. The employer writes a document, usually called a written practice, that sets out its training, experience, examination and recordkeeping rules. A Level III approves it, and the employer signs each certification. Three documents dominate:

• SNT-TC-1A, from ASNT, is a recommended practice: guidance an employer adapts into its own written practice. Because it is guidance, two employers' written practices can differ.
• CP-189, also from ASNT, is a national standard that sets minimum requirements, and the employer writes a certification procedure to meet it. It ties Level III status to holding a current ASNT Level III certificate.
• NAS410, from AIA, is the aerospace standard. It requires a written practice and a named Responsible Level 3, who may come from an outside agency. An outside agency can qualify people, but only the employer can certify them. EN 4179 is its European counterpart.

Central certification means an independent body examines and certifies the individual. ISO 9712 is the international standard for this, and national schemes such as PCN, run by BINDT in the UK, are built on it. In the United States, ASNT's newer ASNT 9712 program is built on ISO 9712:2021, and ASNT says its older ACCP program is being retired, with the last active certifications expiring in 2029.

A central certificate stays with the person, but it does not replace the employer. The employer still has to confirm you can do its particular work to its procedures and authorize you to do so.

Which one do you need?

You usually do not choose. The customer, contract, code or regulator chooses, and your employer's program follows. Aerospace work generally runs on NAS410 or EN 4179. Much general industrial work in the United States runs on SNT-TC-1A or CP-189. Central certification is common in many countries outside the United States and on some international projects. Naval, nuclear and other regulated work can add rules of its own. The two worlds also overlap: both SNT-TC-1A and NAS410 give employers a way to take credit for certain outside certificates for some examinations, if the written practice allows it.

Training and experience hours

Every scheme asks for documented formal training plus documented experience, and the figures differ by method, level and scheme. The number that governs you is the one in your employer's written practice or your certification body's rules. As an illustration only, here are two methods from the current editions in our reference library:

Sources: SNT-TC-1A 2024 edition, Table 6.3.1 A; NAS410 Revision 6 (December 2025), Tables 1 and 3. Illustration only. SNT-TC-1A hours are recommendations an employer may adjust in its written practice, for example for education. Check the current edition before relying on any figure.

Both documents let a person go straight to the second level by meeting the combined requirement. Training normally comes first or runs alongside on-the-job work, and your experience has to be recorded as it happens. NAS410 is specific about what those records show: the individual, date, activity, hours, and who was observing.

Examinations and vision

For Level I and II, expect three parts in each method:

• General: the principles of the method. Closed book.
• Specific: the equipment, procedures, codes and acceptance criteria you will actually use.
• Practical: a hands-on demonstration on test samples, graded with a checklist.

Both documents aim for an 80% average. SNT-TC-1A recommends at least 80% as a composite and on the practical, with no written exam under 70%. NAS410 requires at least 70% on each exam, an average of at least 80%, and finding all the specified discontinuities on the practical. An exam can never be given by the candidate or by a subordinate.

A vision check comes with it. Near vision is tested every year, and color or contrast perception at intervals of up to five years under both documents. People with limited color perception are not automatically ruled out; the question is whether they can do the method in question, and the Level III decides under the written practice.

Reaching Level III

Level III comes after real time at the bench or in the field. NAS410 Revision 6 asks for four years of Level 2 experience with no relevant college study, two years with a two-year engineering or physical science program, or one year with a three- or four-year degree, and it offers a credit system as an alternative. SNT-TC-1A recommends a similar one, two or four years beyond the Level II requirements, depending on education. Check the wording in your edition, because the two are not counted identically.

Level III examinations also go further. Both schemes add a basic exam covering the scheme itself, materials and processes, and other NDT methods, which is taken once. In NAS410, the Level 3 practical is writing a procedure or work instruction, with a hands-on exam as well if the person will accept product. Under CP-189, the Level III route runs through a current ASNT Level III certificate.

Keeping it current

• Recertification. SNT-TC-1A recommends a maximum interval of five years, and NAS410 requires recertification at least that often. NAS410 Level 1 and 2 recertify by specific and practical exams; Level 3 may use a credit system instead. NAS410 also requires a documented annual proficiency review.
• Changing jobs. Under employer-based schemes, certification ends when employment ends. Your hours and training records can still count, if the new employer's Level III accepts them, so keep your own copies. Expect to take at least some exams again.
• Central certificates run on their own renewal rules. ASNT describes recertification for ASNT 9712 every five years.

A practical way in

1. Find an employer with a working NDT program, or a technical school NDT course that leads to one. Hours only count when they can be documented and accepted.
2. Ask which scheme the employer uses and read its written practice. It is your real rulebook, and it tells you what counts.
3. Log your hours from day one, and keep copies of training records and certificates.
4. Start with a method your employer actually uses. Many people begin with PT, MT or VT and add UT, RT or ET later.
5. Decide early if Level III is the goal, and plan the study, the basic exam and the experience around it.

Where to look further

• Our NDT acronyms and terms and standards reference pages.
• ASNT's certification site for ASNT 9712 and Level III programs, and asnt.org for SNT-TC-1A and CP-189.
• The Aerospace Industries Association, publisher of NAS410.
• ISO for ISO 9712, and BINDT for PCN.
• Our method guides: UT, RT, ET, MT, PT, VT, AE and leak testing.

Frequently asked questions

How NDT LLC can help

Employers building or repairing a qualification program can work with our team of Level IIIs on written practices and Level III services. Contact us to talk it through.