An interface device for supplying a gas flow for breathing is disclosed herein. The device includes at least one socket for detachably connecting an apparatus for supplying anesthetic agent, at least one gas output opening for delivering the fresh gas to the apparatus, and at least one gas input opening for receiving the fresh gas mixed with anesthetic agent. The device also includes a connection valve and at least four ports in flow communication with the valve, a first port receiving the gas, a second port providing a communication with the output opening, a third port providing a communication with the input opening, and a fourth port providing a communication for breathing, the valve having a first operational state disconnecting communication between the first and second port, and to second operational state providing communication between the first and second port, but also between the third and fourth port.