The relationship between the applied voltage and pulse height in a detector is very complex. Pulse height and the number of ion pairs collected are directly related. As was written, the voltages can vary widely depending upon the detector geometry and the gas type and pressure. The figure schematically indicates the different voltage regions for alpha, beta and gamma rays. There are six main practical operating regions, where three (ionization, proportional and Geiger-Mueller region) are useful to detect ionizing radiation. These reqions are shown below. The alpha curve is higher than the beta and gamma curve from recombination region to part of limited proportionality region due to the larger number of ion pairs produced by the initial reaction of the incident radiation.
Finally, at still higher voltages (above Geiger-Mueller region), the electric field generates a continuous discharge of the medium, with the chamber no longer being sensitive to any incident ionization. This region is not used for detection or measurement of ionizing radiation. If the Geiger tube voltage is increased above the end of the plateau the count rate begins to increase rapidly again, until the onset of continuous discharge where the tube cannot detect radiation, and may be damaged.