Abstract: The prior-art CO.sub.2 adsorbent masses used in oxygen-supplying respirators have the disadvantage that they can be granulated only very poorly. The granules have low strength and a tendency to dusting. The goal of the present invention is to produce harder granules which do not give rise to dusting any longer. This is achieved according to the present invention by adding an alkali salt of an oxo acid, preferably sodium hexametaphosphate, to the calcium hydroxide paste prior to the granulation. The present invention is not limited to this salt, but it is also possible to use alkali salts or other oxo acids, such as orthophosphoric acid, sulfuric acid, hypermanganic acid, chromic acid, and vanadic acid. This leads to a substantial increase in the strength to the calcium hydroxide granules without any reduction of their CO.sub.2 binding capacity.