Abstract: A trigger (18), containing one component (28) of a two component gas generating system and having a headspace (37), is closed by a pressure rupturable membrane (36) and located in an expandable pouch (10), in a reservoir of the other component (19) of the gas generating system, with the membrane (36) facing down. The pouch (10) is inserted into a dispensing container (44) for flowable product, and the container is sealed. Thereafter, the trigger (18) is activated by externally pressurizing the container by back flow of fluid through a dispensing valve (46), either by adding a gas or by adding flowable product, causing the membrane (36) to rupture and the trigger (18) to discharge its contents into the reservoir of the other gas generating chemical (19).