ANSI/ASNT CP-189 is the American Society for Nondestructive Testing's standard for qualifying and certifying nondestructive testing (NDT) personnel. It shares a publisher, a vocabulary and three Roman-numeral levels with SNT-TC-1A, which is why the two are so often confused. The difference is the word in front: SNT-TC-1A is a recommended practice, and CP-189 is a standard.
A standard, not a recommended practice
SNT-TC-1A is written with “should”. It hands the employer a framework — hours, exams, vision, recertification — and expects the employer to adapt it into its own written practice. Two companies can follow it faithfully and still certify differently.
CP-189 is written with “shall” and approved as an American National Standard. Its requirements apply as written. An employer still writes a procedure for its own program, and still certifies its own people, but the minimums are not the employer's to adjust. For a customer, a code body or a regulator, that is the point: a CP-189 certification means the same thing whichever supplier issued it.
Where you meet it
CP-189 turns up where a code or contract wants a fixed rulebook rather than each employer's version of one:
- Nuclear in-service inspection. ASME Section XI, the code for in-service inspection of nuclear plant components, is the classic route to CP-189 for NDE personnel, with its own additional requirements on top. The nuclear qualification guide traces how the federal rules lead there.
- ASME Section V work. The 2025 edition of Section V accepts an employer's written practice built on either SNT-TC-1A (2024) or CP-189 (2024) for work that references its Article 1, with a small number of exceptions for each (T-120(e)). More in the ASME Section V and XI guide.
- Contracts. Owners and prime contractors in power generation and other regulated work name CP-189 in purchase orders and specifications when they want certainty about what a supplier's certifications mean.
What stays the same as SNT-TC-1A
The architecture will be familiar to anyone who runs an SNT-TC-1A program:
- Employer certification. The employer certifies its personnel, and a certification belongs to that employer.
- Three levels. Level I, Level II and Level III, in Roman numerals, with broadly the same division of work: Level I performs to instructions, Level II sets up, interprets and evaluates, Level III owns procedures, techniques and the training and examination of others.
- Training, experience and exams. Organised training, documented experience by method, and written and practical examinations before certification.
- Vision and recertification. Near-vision and color checks, and periodic recertification.
What the 2018 addendum settled
The 2016 edition's Addendum 1, created in August 2018, is short but practical. In outline:
- How training can be delivered. Organised training may be instructor-led, personalised, virtual instructor-led, computer-based or web-based; computer- and web-based training has to track hours and content, with student exams (4.1.1.1). It also defines personalised instruction (2.1.22).
- Central certificates. An employer may accept a valid ASNT NDT Level II certificate for either or both of the general and specific exam requirements, and a valid ACCP Level II certificate for any of the exam requirements, if the Level III has determined that the ASNT exams meet the employer's procedure (6.4, 6.5).
- Passing scores. At least 70% on each employer-administered written exam, at least 80% on each practical, and a composite average of at least 80%, with every certification exam weighted equally (6.6.2).
- The certification record carries the signature of the Level III who verified the candidate's qualifications (9.2.1.6).
- Limited Level II certifications gain notes on experience: counted in actual hours worked in the method, documented by method and hour with supervisor or Level III approval, and with each method's minimum still met when experience spans several (Appendix B).
Running SNT-TC-1A and CP-189 side by side
Many shops certify some people to SNT-TC-1A for general work and others to CP-189 for a nuclear or code customer — sometimes the same technician under both. That is workable if the records never blur:
- Keep separate procedures (or clearly separate sections) for each, and cite the right one on every certification.
- Record which document and edition each certification was issued under, because a customer auditing a CP-189 job will ask.
- Track each certification's own dates. The two may not expire together, and neither does a vision exam care which scheme it is serving.
- When a new edition arrives, check both procedures against it — a change in one does not change the other. The standard revisions guide covers the routine.
How TRACE handles it
In TRACE every certification cites the written practice or procedure it was issued under, recorded on the company and named on the certificate, so SNT-TC-1A and CP-189 certifications for the same technician never read as one another. Each keeps its own expiry, the vision exams and recertification dates sit beside them, and the dashboard and reminder digest show what is coming due before it lapses.
Certifications issued by an outside body — an ASNT Level III, for example — can be recorded as third-party certifications with their certificate number and tracked to expiry the same way. See what else TRACE does.
Frequently asked questions
What is the difference between CP-189 and SNT-TC-1A?
Both are published by ASNT, both are employer-based and both use Levels I, II and III. SNT-TC-1A is a recommended practice: guidelines written with "should" that each employer adapts in its own written practice. CP-189 is an ANSI-approved standard written with "shall", so its requirements apply as written and every employer following it is held to the same rules.
What is the latest edition of CP-189?
ASME Section V's 2025 edition cites ANSI/ASNT CP-189 (2024 Edition), which indicates a 2024 edition has been published; the edition before it was 2016, with an addendum in 2018. Confirm the current edition with ASNT, and check which edition your contract or code names — that is the one you are held to.
Who certifies personnel under CP-189?
The employer. CP-189 standardises the requirements, but certification is still the employer's written testimony that the person is qualified, under the employer's own procedure.
What passing scores does CP-189 require?
Under the 2016 edition as amended by its 2018 addendum, each employer-administered written exam needs at least 70%, each practical at least 80%, and the composite average at least 80%, with all certification exams weighted equally. Check the edition you work to.
Checked against
- ANSI/ASNT CP-189, 2016 edition, Addendum 1 (created August 2018) — the addendum pages only
- ASNT SNT-TC-1A, 2024 edition, with the 2025 addendum
- ASME Boiler and Pressure Vessel Code Section V, 2025 edition, Article 1 (T-120), which cites CP-189 (2024 edition)
This guide summarises the documents above in our own words to help you find your way around them. It is not a substitute for them: requirements change between editions and contracts add their own, so check every figure against your own licensed copy and your written practice before you rely on it.
Named for reference only. TRACE is an independent product: it is not affiliated with, endorsed by, sponsored by or accredited by ASNT (publisher of CP-189 and SNT-TC-1A), ANSI or ASME, or by any other organization whose standards or programs it describes. Their names and marks are their own.