A storage and mixing device is illustrated and described. The device can include first and second separate containers each defining a distinct internal cavity. The first container can be movable (e.g., rotatable) relative to the second container between a first position and a second position. In the first position, the cavities can be substantially sealed from one another. In the second position, a first gas forming ingredient in one of the cavities can mix with a second gas forming ingredient in the other cavity to form a gas, such as chlorine dioxide gas. The device can have one or more filtered openings to allow gas generated by mixing the first and second gas forming ingredients to escape into the ambient environment.