Abstract: Apparatuses for producing and dispensing a reaction mixture include a mixing head for mixing the reaction components that are fed via two supply lines. The apparatuses also include a decompression system to relieve pressure from the supply lines to avoid the reaction components seeping into the mixing head. The decompression system includes two pressure vessels each with two sides, separated by a membrane. One of these sides forms an expansion chamber for the reaction component, while the other side is connected to a pneumatic system. With this pneumatic system, the expansion chamber can be pressurized before the production of the reaction mixture. After the production of the reaction mixture, the pressure can be relieved.