The European XFEL SASE3 undulator beamline instrumental end-stations make use of a gas-based device to control the transmitted intensity of the free-electron laser (FEL) photon beam. This device is specifically designed to provide the required level of attenuation without compromising the general stability of the ultrahigh vacuum (UHV) conditions of the surrounding beamline vacuum sections. This Technical Note gives a general description of the most relevant aspects that characterize the control of the gas attenuator device. In particular, it is especially focused on the safety interlock implementation and the implications that it imposes on the operative characteristics of the device.