A device with a water trap. The device has a gas sensor and is designed to send a gas sample flow through the water trap (2) and to feed it to the gas sensor (3). The water trap (2) is designed to be separably connected to the device. The device has a mount for connection to the water trap. The water trap (2) has a radio frequency marking (5). The device has a radio frequency detection device (6) with a detection area (7) for the radio frequency marking, which is designed to detect the radio frequency marking in the detection area and to generate a marking signal, which represents marking information of the radio frequency marking. The device is designed to be controlled as a function of the marking signal.