Sudden oxidation or decomposition substance concentrating in the air causing an explosion. endangered areas are divided into zones defined by the frequency of the occurrence and the duration of the presence of an explosive Small solid particles in the atmosphere, which settle due to their own weight, however, can stay airborne in the atmosphere for some time as a dust/air mixture./air mixture; the following definitions only apply to the device group II.
Zone 20: area in which a dangerous explosive atmosphere generated by clouds of dust in the air exists permanently, for longer periods of time or frequently. The presence of personnel and the performance of work are not possible in zone 20.
Zone 21: area occasionally susceptible to the formation of a dangerous explosive atmosphere in the form of a cloud of Dust, fibres or suspended matter that can burn or smoulder in the air and generate explosive mixtures with the air in the presence of atmospheric pressure and at normal temperatures. in the air during State in which the devices, protection systems and components fulfil their intended function within their design parameters..
Zone 22: area in which, during normal operation, an explosive atmosphere in the form of a cloud of combustible dust in the air normally does not occur or only for a short period of time.