A closure device for use with a container having a container neck comprises a cap member having a first fluid chamber and a housing having a second fluid chamber. The housing is arranged to move relative to the cap member between a first armed position and a second firing position. The housing includes a first plug member adapted to close a bottom aperture in the first fluid chamber in the first armed position. The cap member includes a second plug member adapted to close a bottom aperture in the second fluid chamber in the first armed position. In the second firing position the first plug member is removed from the aperture in the first fluid chamber and the second plug member is removed from the aperture in the second fluid chamber.