A rotary sealing device for connecting a fixed gas supply pipe to a tube rotating about its axis. It comprises a first rotary member for receiving the fixed pipe, a second rotary member for receiving and sealing the rotary pipe and fixed to the first member, and a filter placed in a chamber made in the aforementioned members and forming an obstacle to the gas flow and consequently to an overpressure of said gas, opposing the entry into the said chamber of gas coming from outside the device.