Method for distinguishing an arc from a luminous gas containing at least metal vapor

A device for distinguishing an arc from a luminous gas including a metal vapor, the device comprising:

• at least one light-sensitive element configured to sense light in a monitoring region;
• a measuring device configured to measure a first intensity Iλ1 of sensed light at a first wavelength Iλ1 and to measure a second intensity Iλ2 of the sensed light at a second, greater wavelength Iλ2;
• an evaluation unit configured to determine a ratio Iλ1/Iλ2 between the first intensity Iλ1 and the second intensity 1λ2 and to associate the sensed light with the arc if the ratio Iλ1/Iλ2 is greater than a specifiable first threshold value and/or with the luminous gas if the ratio Iλ1/Iλ2 is less than a specifiable second threshold value.