BECKHOFF CX50x0 - Manual (Page 16)

Classification of surrounding atmosphere into zones
12 CX50x0 units in potentially explosive areas
4.5 Classification of surrounding atmosphere into zones
Potentially explosive areas must be classified into zones in which the atmosphere (in the case of potential
danger) can become explosive.
This classification takes into account the various dangers due to explosive atmospheres according to the
probabilities and enables the implementation of explosion protection with regard to the boundary conditions for
safety and economy.
Potentially explosive areas
Zone 0 An atmosphere where a mixture of air and flammable substances in the form of gas, vapor or
mist is present frequently, continuously or for long periods.
Zone 1 An atmosphere where a mixture of air and flammable substances in the form of gas, vapor or
mist is likely to occur in normal operation occasionally.
Zone 2 An atmosphere where a mixture of air and flammable substances in the form of gas, vapor or
mist is not likely to occur in normal operation but, if it does occur, will persist for only a short
period.
Zone 20 An atmosphere where a cloud of combustible dust in the air is present frequently,
continuously or for long periods.
Zone 21 An atmosphere where a cloud of combustible dust in the air is likely to occur in normal
operation occasionally.
Zone 22 An atmosphere where a cloud of combustible dust in the air is not likely to occur in normal
operation but, if it does occur, will persist for only a short period.