A non-spilling, detachable pouring spout is configured to transfer liquid from a non-vented filling container to a receiving container. The spout has a spout body defining a first hollow passageway extending from an open first end to an open second end, wherein this open passageway having a generally tubular hollow inner conduit positioned within the first hollow passageway and defining a second hollow passageway. An intermediate sleeve is received in the spout and seals against portions of the spout body and the inner conduit so as to variously control the flow of materials out of the spout body, preferably the flow of liquid out of the spout and air into the spout as a venting system. The movement of said sleeve may be controlled by movement of an external sheath and may include child-resistant features. The preferred spout may achieve smooth air venting and liquid flow, and minimizes transverse/sideways flow and openings that tend to cause splash and leaks. The preferred spout does not use any O-ring members, which are prone to failure when used with gasoline, but instead uses a slidable sleeve with inner and outer seal surfaces provided by a flared or bell-shaped seal member.