The spout includes a first and a second member. The first member includes an elongated and generally tubular first main body having two segregated and parallel internal passageways, one being an air duct and the other being a liquid duct. Both ducts are substantially straight and substantially unobstructed along the entire first main body but the air duct ends with at least one constricted opening through which the air circuit exits the air duct. A valve is juxtaposed to the rear end of the first main body and is made integral therewith. The valve engages a valve seat provided at the rear end of a tubular inner conduit inside the second member and in which a rear section of the first main body is slidingly axially movable. The valve is normally maintained closed by a biasing element. The spout may be provided with a child resistant closure (CRC) device.