ANSI/ESD STM5.2 was the ESD Association standard defining the component level machine model test. The machine model was introduced to represent a hazard that the human body model does not cover: a discharge from a metallic object such as a tool, a test handler or a soldering iron, in which the source has almost no series resistance and the stored energy is therefore delivered to the device in a very short and comparatively severe pulse. Because the source impedance is low, a device that withstands a given voltage under the human body model may fail at a much lower voltage under the machine model, and for a period the machine model was widely used in Japan and in parts of the semiconductor industry as an additional classification. Doubts about the reproducibility of the waveform and about how well the model represents real handling led to its abandonment for new qualification programmes by most manufacturers, and the standard is retained mainly for historical classification data.