Understanding the differences between SNT‑TC‑1A (2024) and CP‑189 (2024) is one of the most important skills for anyone preparing for the ASNT Level III Basic Exam. These two documents look similar on the surface—they both deal with qualification and certification of NDT personnel—but they serve very different purposes, use different authority levels, and create different administrative obligations for employers and Level III personnel.
The exam expects you to know not only what each document says, but how they differ, why they differ, and how those differences affect real‑world certification programs. This guide walks through those distinctions in depth, using the attached 2024 editions of both documents as the foundation.
Why These Two Documents Matter for the Exam
The ASNT Level III Basic exam tests your ability to think like an NDT administrator. This means understanding how certification programs are created, evaluated, and audited.
What the Exam Expects You to Know
- ✔ Knowing which document governs which requirement
- ✔ Knowing when a requirement is mandatory vs recommended
- ✔ Knowing how to evaluate certification scenarios
- ✔ Knowing how to identify non-compliance
- ✔ Knowing how to build or audit a certification program
SNT-TC-1A and CP-189: The Two Pillars
These two documents form the foundation of employer-based NDT certification programs. The exam frequently presents real-world scenarios where you must determine the correct administrative decision.
- Is this allowed under SNT-TC-1A?
- Is this allowed under CP-189?
- Is this certification valid?
- Does this training count?
- Does this experience count?
- Who must approve this?
To answer correctly, you must understand the philosophy behind each document.
The Core Difference: “Should” vs “Shall”
SNT-TC-1A (2024)
Uses the word “should”.
It is a Recommended Practice.
CP-189 (2024)
Uses the word “shall”.
It is an American National Standard.
Exam Tip
When answering Basic exam questions, always ask yourself:
- Is the question referring to SNT-TC-1A?
- Or is it referring to CP-189?
If it is CP-189, remember: the requirement cannot be modified.
Purpose and Intent: What Each Document Is Designed For
SNT-TC-1A (2024)
A flexible guideline for employers to build their own certification program.
CP-189 (2024)
A strict certification standard defining minimum requirements for NDT and PdM personnel.
Certification Documents: Written Practice vs Certification Procedure
SNT-TC-1A – Written Practice
Employers must create a Written Practice that defines how their certification program operates.
CP-189 – Certification Procedure
Employers must develop a formal Certification Procedure in accordance with the standard.
Levels of Qualification
Both SNT-TC-1A and CP-189 define three primary levels of NDT qualification:
- Trainee – Individual undergoing training but not yet certified
- Level I – Performs specific calibrations and tests under supervision
- Level II – Evaluates results and interprets indications
- Level III – Responsible for program administration and certification oversight
The ASNT Level III Basic exam tests your ability to understand how these roles interact within a certification program.
Exam Strategy Tip
When analyzing certification scenarios in the exam, always ask:
- Which document governs this requirement?
- Is flexibility allowed?
- Is the requirement mandatory?
If the question references CP-189, assume the requirement is a mandatory minimum.
Levels of Qualification: Authority Differences
Both SNT-TC-1A and CP-189 define four certification levels: Trainee, Level I, Level II, and Level III. However, the level of authority and restrictions differ significantly between the two documents.
Trainee
SNT-TC-1A
“A trainee should work with a certified individual… and should not independently conduct, interpret, evaluate, or report the results of any NDT.”
Recommendation — not mandatory.
CP-189
“Trainees shall not independently conduct any tests or write a report of test results.”
Mandatory prohibition.
Level I
SNT-TC-1A
Level I personnel may perform specific tests and evaluations according to written instructions.
CP-189
Level I personnel may perform tests and, with prior written approval of a Level III, may perform specific interpretations.
Level II
Both documents generally agree on Level II responsibilities:
- Set up and calibrate NDT equipment
- Conduct inspections and tests
- Interpret and evaluate results
- Train Level I personnel and trainees
However, CP-189 requires strict compliance with procedures approved by a Level III.
Level III
SNT-TC-1A
“Should have sufficient technical knowledge… capable of developing, qualifying, and approving procedures.”
Flexible guidance.
CP-189
“Shall have the skills and knowledge to establish techniques, interpret codes and standards, designate techniques, and verify the adequacy of procedures.”
Level III personnel must hold a valid:
- ASNT NDT Level III certificate
- ACCP Professional certificate
- PdM certificate
- ASNT 9712 Level III certificate
Mandatory credential requirement.
Training Requirements: Flexibility vs Minimums
SNT-TC-1A (2024)
Training hours listed in Table 6.3.1A are recommendations.
CP-189 (2024)
Training hours listed in Appendices A and B are minimum requirements.
Experience Requirements: Recommended vs Mandatory
SNT-TC-1A
Experience hours are recommended guidelines.
- Employers may modify experience hours
- Equivalent experience may be accepted
- Lab hours may count toward experience (2024 update)
CP-189
Experience hours are mandatory minimums.
“Any claimed training or experience that is not documented and cannot be verified shall be considered invalid.”
Strict documentation requirement.
Exam Strategy Tip
When answering Level III Basic exam questions, always determine:
- Is the requirement coming from SNT-TC-1A?
- Or from CP-189?
If the question references CP-189, assume the requirement is a mandatory minimum.
Examination Requirements: Flexibility vs Enforcement
Both SNT-TC-1A and CP-189 require certification exams, but the level of flexibility differs significantly.
SNT-TC-1A (2024)
The recommended certification examination system includes:
- General examination
- Specific examination
- Practical examination
- Vision examination
CP-189 (2024)
The following examinations are mandatory:
- General examination
- Specific examination
- Practical examination
- Vision examination (strict requirements)
Outside Agencies and Level III Services
Some employers use outside organizations for examination services or Level III support. SNT-TC-1A and CP-189 treat this differently.
SNT-TC-1A
A recommendation was added allowing acceptance of an outside supplier for examination services.
Recommended practice — not mandatory.
CP-189
The employer must evaluate any outside organization providing certification services.
This evaluation must be documented.
Mandatory evaluation and documentation.
Certification Validity, Expiration, Suspension, and Revocation
Certification management is another area where the documents differ significantly.
SNT-TC-1A
Certification intervals are typically recommended as five years.
- Employers may modify certification intervals
- Employers define suspension conditions
- Employers control reinstatement procedures
Employer-controlled certification lifecycle.
CP-189
Certification lifecycle rules are mandatory and include:
- Certification expiration rules
- Suspension requirements
- Revocation procedures
- Reinstatement conditions
These may be triggered by:
- Vision exam failures
- Interrupted service
- Misconduct
- Expired certification
Strict compliance requirements.
Level III Exam Strategy Tip
When answering administrative scenario questions, always ask:
- Is the requirement coming from SNT-TC-1A?
- Or from CP-189?
If the question references CP-189, assume the rule is a mandatory minimum that cannot be reduced.
Record Keeping: Flexible vs Strict
Record keeping is essential for maintaining certification programs. However, SNT-TC-1A and CP-189 treat documentation requirements very differently.
SNT-TC-1A
Record keeping is generally recommended rather than strictly defined.
CP-189
Record keeping requirements are mandatory and must be defined within the certification procedure.
Predictive Maintenance (PdM): Included vs Not Included
Another important difference between the two documents involves Predictive Maintenance (PdM) personnel certification.
CP-189
CP-189 explicitly includes certification requirements for Predictive Maintenance (PdM) personnel.
From the document:
PdM certification is covered.
SNT-TC-1A
SNT-TC-1A focuses only on NDT personnel certification and does not include Predictive Maintenance (PdM).
PdM is outside the scope of this document.
Level III Basic Exam Tip
Questions about PdM certification requirements usually refer to CP-189.
If the scenario mentions Predictive Maintenance personnel, the correct reference document is typically CP-189.
13. Summary Table: SNT‑TC‑1A vs CP‑189
| CATEGORY | SNT‑TC‑1A (2024) | CP‑189 (2024) |
|---|---|---|
| Document Type | Recommended Practice | American National Standard |
| Authority Level | Flexible guidelines | Mandatory minimums |
| Language Used | “Should” | “Shall” |
| Employer Document | Written Practice | Certification Procedure |
| Training Hours | Recommended | Mandatory minimums |
| Experience Hours | Recommended | Mandatory minimums |
| Exams Required | Recommended | Mandatory |
| Vision Requirements | Annual, recommended | Mandatory, no eye drops |
| Level III Requirements | Broad familiarity | Must hold valid ASNT/ACCP/9712 Level III |
| Trainee Restrictions | Should not work independently | Shall not work independently |
| Outside Agency Use | Recommended documentation | Mandatory evaluation & documentation |
| Certification Validity | Employer-defined | Strict rules |
| Record Keeping | Flexible | Mandatory |
| PdM Personnel | Not included | Included |
How These Differences Appear on the Level III Basic Exam
The ASNT Level III Basic exam frequently tests whether candidates can correctly interpret the differences between SNT-TC-1A and CP-189.
Most questions are presented as administrative scenarios where you must determine whether a certification action is valid.
What the Exam Typically Tests
- Whether a requirement is mandatory or recommended
- Whether certification is valid under CP-189
- Whether a Written Practice can override SNT-TC-1A
- Whether training or experience can be accepted
- Whether a Trainee or Level I is allowed to perform certain tasks
- Whether an outside Level III service is properly documented
- Whether vision examination rules were followed
Common Exam Traps
Many questions are designed to test whether you recognize subtle violations of CP-189 requirements.
Trainee Working Alone
A trainee performing tests independently.
Violation under both documents, but a mandatory violation under CP-189.
Level I Interpreting Results
Level I evaluates test results.
Allowed only with prior written approval of a Level III under CP-189.
Undocumented Experience
Candidate claims experience but records cannot be verified.
Invalid under CP-189. Possibly acceptable under SNT-TC-1A.
Missing Vision Exam
Certification issued without vision examination.
Invalid certification under CP-189.
Certification Start Date
When does certification officially begin?
Tied to the Certifying Authority signature in the 2024 editions.
Final Thoughts
SNT-TC-1A and CP-189 are not competing documents — they are complementary.
However, for the ASNT Level III Basic examination, understanding the differences between these two documents is critical.
SNT-TC-1A
Flexibility
Recommended practice that allows employers to customize certification programs.
CP-189
Mandatory Minimums
American National Standard establishing strict certification requirements.
Why This Matters for Level III Candidates
Understanding these distinctions allows you to:
- Evaluate NDT certification programs
- Identify non-compliance
- Interpret administrative exam scenarios correctly
- Think like an NDT Level III administrator
This is exactly what the ASNT Level III Basic exam is designed to measure.
Prepare for the ASNT Level III Basic Exam
If you want to strengthen your exam readiness further, practicing with scenario-based questions built from SNT-TC-1A and CP-189 can significantly improve your ability to apply these rules under pressure.
Our preparation program includes 2500+ practice questions, detailed explanations, and one-to-one guidance for Level III candidates.
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