The invention concerns a sample chamber used for monitoring the concentrations of components of additives in a printing process liquid for maintaining predetermined desired concentrations of components of additives in a printing process liquid, wherein the actual concentrations of components are determined followed by redosing of measured components to a predetermined desired concentration. In one embodiment, a line-of-sight volume is a grid volume that has the same size and shape as it corresponding game element. The duct main body is pivotably installed to at least one of both side surfaces of the refrigerating chamber.