Abstract: A release device for an air cushion or thermal insulation barrier of a double or multi glazed glass unit comprises interfitting first and second members which are movable relative to one another, the first member having associated with it a pin or striker which is movable with the first member from an inoperative position to an operative position to crack or penetrate one or more glass panels of the unit, the device has one or more ventilation orifices to enable release of the sealed air cushion or thermal insulation barrier between the panes of a glazed unit. To limit the relative movement of the first and second members of the device there is within the device interfitting projections. The device, which may include one or more springs, may be mounted on a support structure for movement from an inoperative position to an operative position.