A method and apparatus to automatically produce blocks of solid CO.sub.2 at low pressure. The apparatus includes at least one closed mold coupled to a liquid CO.sub.2 conditioner and a CO.sub.2 gas recovery system, and a control panel for automatic operation. The method consists in supplying liquid CO.sub.2 to this mold at a low pressure in order to fill the mold with CO.sub.2 snow of low density during a definite period of time, to then raise the pressure inside the mold to an intermediate pressure by supplying liquid CO.sub.2 at this pressure (and at a temperature of approximately -40.degree. C.) to form a dense mass of solid CO.sub.2 which after a definite time will block the admission of CO.sub.2 to the mold, causing a significant pressure drop that is used to create a signal to automatically close off the supply of liquid CO.sub.2 and finalize the production cycle of the block.