Leak testing is a procedure used to identify manufacturing defects to checks the integrity of products and improve safety. These leak testing procedures are defined and specified by a variety of standard organizations.Pipeline leak detection is used to determine to check where a leak has occurred in systems which contain liquids and gases. Methods of detection include hydrostatic testing, infrared, and laser technology after pipeline erection and leak detection during service.A leak is a flow of gas (or liquid) through the wall of a vessel (via an imperfection such as a hole, crack or bad seal) Leaks require a pressure difference to generate the flow; they always go from higher pressure to lower pressure. Leaks are pictured as going from positive pressure (inside an object) to outside (at atmospheric pressure). This is not always the case ( leak could be from atmosphere to inside an evacuated object), but it helps to think about it this way because the units and terminology are based on this model.