A device that assists with equalizing air pressure within a bottle with the atmospheric air pressure as liquid is being poured from the bottle and includes one or more relatively short air tubes. The air tubes are situated with an upper inlet rim of the air tubes located flush with or relatively near the bottle rim. Whether an insert or integrated into the manufacture of a container, the one or more air tubes that extend partially into the container allow air to pass into the container as the liquid exits the container. The pressure equalizer not only minimizes or prevents the common glugging effect, but it allows liquid from a bottle to be poured smoothly at any angle and orientation. A cap incorporating a detachable pressure equalizer is also described.