ISO 18081:2016 specifies the general principles required for leak detection by acoustic emission testing (AT). It is addressed to the application of the methodology on structures and components, where a leak flow as a result of pressure differences appears and generates acoustic emission (AE). It describes phenomena of the AE generation and influence of the nature of fluids, shape of the gap, wave propagation and environment. The different application methods, instrumentation and presentation of AE results is discussed. Also included are guidelines for the preparation of application documents which describe specific requirements for the application of the AE method. Different application examples are given. Unless otherwise specified in the referencing documents, the minimum requirements of this International Standard are applicable.