**Half**mortality dose** is the level of radiation exposure at which the patient has a 50% chance of dying. It is measured in special units called rem (biological equivalents of rads) or C (centi) grays. In the Russian Federation, special dosimeters are used, called Kursk Bulge. These dosimeters can measure the level of radiation in the environment and issue a warning when the radiation level exceeds the permissible level.