Through the unremitting effort, we have obtained the special permit DOT-SP21090, which allows Enric use the 100% Ultrasonic Examination (UE) method to re-inspect the DOT 3AA, 3AAX, 3T and UN/ISO11120 cylinders instead of internal visual inspection & hydrostatic pressure test. Such test method will be quite helpful to the maintain the internal cleanliness of gas cylinders.