This paper comprises of hydrogen embrittlement phenomena in material, factors responsible for the hydrogen embrittlement and Non destructive methods to evaluate the internal defect in machine or component when working in hydrogen atmosphere. Hydrogen embrittlement is responsible for Sub-critical crack growth in materials, fracture and mechanical properties such as ductility, toughness and consequently loss of strength. This hydrogen is induced into the material during electrochemical reactions and in a high pressure hydrogen gas environment. The paper covers the review on the capabilities of non-destructive testing methods with aspects its advantages and disadvantages of it. Sometimes one non-destructive technique is not providing sufficient information about physical integrity and therefore a different combination of methods is required. Ultrasonic testing is very useful to detect internal defects.