Catching a flaw early means fixing it on your schedule—not after a leak, breakdown, or shutdown forces the issue.
What Is Nondestructive Testing?
Discover the technologies, methods, and standards that keep infrastructure, products, and transportation safe and reliable.
Why NDT Matters
Nondestructive testing involves inspecting and evaluating materials, components, and assemblies without harming them, and often without even taking them out of service. Regular NDT inspections are at the core of proactive maintenance programs supporting our most vital industries.
NDT in Action: Real-World Impact
Done well, NDT catches problems while they're still small, cheap, and easier to plan around. Done poorly or skipped altogether, the same small problem can turn into a safety failure, a shutdown, or worse.
How Does NDT Work? An Overview of NDT Methods
To perform NDT with precision, technicians need to inspect materials and components from the outside, inside, and even through solid, semi-solid, or liquid materials.
Some methods are best suited for catching surface problems, while others are designed to find flaws hidden deep inside a component. Choosing the right one takes real expertise: a trained specialist considers the material, its shape, and where a flaw, or defect, is likely to be before deciding how to inspect it.
Not every anomaly an inspector finds means trouble. Part of that same expertise is knowing the difference, deciding whether something needs to be repaired, rejected, or simply logged for continued monitoring.
That level of precision is possible thanks to a wide range of media, technologies, and equipment built for exactly this kind of work.
NDT, NDE, and NDI: What's the Difference?
You'll often see nondestructive testing (NDT) called by other names, and the differences are subtle enough that even people in the field sometimes use them interchangeably:
Nondestructive testing (NDT) is the term used most widely across the industry. In NDT, a technician applies scientific techniques and methods to detect flaws in materials and structures.
Nondestructive inspection (NDI) means largely the same thing as NDT. Some industries, aerospace and defense especially, simply prefer this term.
Nondestructive evaluation (NDE) carries a slightly different emphasis: instead of only detecting a flaw, it points to interpreting what that flaw means, how big it is, how serious it is, and whether the part is still fit to use.
NDT vs. Destructive Testing
Destructive testing (DT) determines how and when a material or component will fail by subjecting it to increasing stress until it breaks, cracks, deforms, or otherwise fails. Because the test permanently damages or destroys the specimen, it is typically performed on sample pieces during product development, quality control, or certification—not on finished products already in service. You can sacrifice a test coupon from a production batch, but you can't destroy an aircraft wing, an operating pressure vessel, or a bridge carrying traffic just to confirm it's safe.
Nondestructive testing (NDT) evaluates the condition, integrity, and performance of a material or component without causing damage. Using methods such as ultrasound, radiography, eddy current, magnetic particle, liquid penetrant, and visual inspection, NDT detects flaws, measures properties, and verifies quality while leaving the part fit for service. Because the component remains intact, inspectors can examine the actual aircraft wing, pressure vessel, pipeline, bridge, or weld that people rely on—not just a representative sample. That's why NDT is used throughout an asset's entire lifecycle, from manufacturing and installation to routine maintenance and life extension.
Where Is NDT Used?
NDT is used across nearly every industry where safety, quality, reliability, compliance, or the ability of a material to hold up under stress matters, including aerospace, energy, infrastructure, manufacturing, and transportation. Anywhere a hidden flaw could put people, property, uptime, or regulatory standing at risk, there's likely an NDT professional inspecting for it.
See NDT in action across each industry:
“NDT is unpredictable, and that’s what I love about it. Every year, every month, there’s a new challenge or a customer that wants something that nobody else can provide—and you get to figure out how to make it happen for them.”
Jesse Groom
Innovative Tech Lead, NDT
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Who Performs NDT?
Nondestructive testing is performed by highly trained professionals who inspect the materials, components, and infrastructure that keep the modern world running. They work in various industries, helping ensure that critical assets are safe, reliable, and fit for service.
NDT professionals come from many different backgrounds. Some begin their careers in the trades or military, while others transition from engineering, manufacturing, education, or entirely different fields. What unites them is a shared expertise: applying inspection methods with precision, interpreting complex data, solving problems in the field, and communicating findings that organizations depend on to make informed decisions.
What Are the Different Roles in NDT?
Most NDT careers build around roles based on NDT certification, which is commonly organized into three levels: I, II, and III. Only Levels II and III are certifications issued directly by ASNT. Level I is typically an informal term for someone early in their training, working under supervision, rather than its own standalone credential.
Trainee: sometimes called a Level I, learning to perform specific NDT inspections and procedures under supervision
Level II Technician: working independently, setting up and calibrating tests, and running inspections
Level III Manager: developing and qualifying NDT procedures, training others, and managing an inspection program
Depending on someone's background and prior experience, it's common to enter at a different point and move between levels as skills and certifications grow, and each level reflects the degree of responsibility rather than just a number.
These three roles make up the primary workforce and handle most of the hands-on testing, but the field extends well beyond them. Instructors train the next generation of inspectors, consultants advise organizations on their inspection programs, and researchers develop the techniques and technologies of the future.
Explore NDT Career Pathways
Why Do NDT Certifications Matter?
For many NDT professionals, certification is more than a credential—it's a requirement. Employers, regulators, and customers often require inspectors to hold Level II or Level III certification before they can perform critical inspections. Certification verifies that an individual has met established standards for training, experience, and examination, demonstrating the knowledge and competence to perform NDT safely and effectively.
For more than 50 years, ASNT has been a global leader in NDT certification. Its internationally recognized certification and qualification programs support professionals across a wide range of industries, inspection methods, and career stages, helping employers and asset owners identify qualified personnel with confidence.
Explore ASNT Certifications
What Determines NDT Certification Requirements?
Behind every certification is a written standard that defines exactly what it takes to earn it, from required training and hands-on experience to the knowledge and skills candidates must demonstrate. These standards ensure certification is consistent, credible, and recognized across employers and industries.
Learn More about ASNT Standards“ASNT is creating a safer world—together, as a community, we make the world a little bit safer. There’s no greater purpose in my mind. ASNT membership has benefited me in so many ways, from finding a job to advancing at that job to now being on the board of directors. If you’re willing to share with the industry and be an advocate, ASNT gives you the platform to do so."
Emilie Peloquin
Director of Global Advanced Product Support
Frequently Asked Questions
Certification isn't always a straight line from an entry-level role to Level II to Level III; it depends on your education and experience.
Most people progress toward Level II first: a combination of training, hands-on experience, and passing written and practical exams. But someone with a relevant engineering or science degree and enough documented work experience can apply directly for Level III certification without first holding ASNT's own Level II credential.
Learn more about the different NDT career pathways to find what's next step makes the most sense for you or explore the different ASNT certification options available.
You'll often see NDT roles described as Level I, II, and III. In practice, only Level II and Level III are certifications ASNT issues directly.
"Level I" is more of an informal term for someone early in their training, performing specific tasks under supervision, than an actual certification level.
ASNT certifications start at Level II and Level III, and both combine education, documented work experience, and exams, though the exact mix depends on your background.
Requirements vary by education level, method, and program, so compare ASNT Certifications for the specifics that apply to your situation for each program.
SNT-TC-1A is an ASNT guideline for employer-based certification, where a company trains and certifies its own inspectors against a written practice it develops.
ISO 9712 is an international standard for central certification, where an independent, accredited body certifies inspectors directly rather than the employer.
ASNT's own certification programs reflect this same split: ASNT NDT follows the employer-based model built on SNT-TC-1A, while ASNT 9712 follows the ISO 9712 central certification model. The right choice depends on your industry and work location.
You can look up whether an individual holds a current ASNT certification through ASNT's certification database. This is the most reliable way to confirm someone's credentials are active.
Getting started usually means finding a training program that fits your background.
ASNT offers multiple education courses, including webinars, eLearning, instructor-led courses, and certification prep across the different NDT methods, so you can find something that matches your schedule and experience level.
Training can also be provided through technical and community colleges or training organizations. Explore our education directory to find a program near you.
Keep Exploring NDT
Have more questions about nondestructive testing? Explore the rich information and resources available through the American Society of Nondestructive Testing.
