An electric machine such as for example, an electric generator, is provided having a lock system which enables a monitoring device to be housed in the machine such that the generator is not required to be purged. The machine, which can be filled with a gas, with a housing, wherein a first chamber is arranged on the housing, wherein a first flap valve is arranged between the housing and the first chamber, creating a fluidic connection between said housing and first chamber, and a second chamber which is arranged on the first chamber, wherein a second flap valve is arranged between the first and the second chambers, creating a fluidic connection between said first chamber and second chamber, wherein a monitoring device for inspection purposes is provided in the housing.