Abstract: A gas regenerator is provided having for the clean air a set of two adjacent parallel flow paths having hot and cold ends, and for the waste gas a set of two adjacent parallel different flow paths, having hot and cold ends, the air and waste gas being separated while passing through the mass storage and heat transfer material of the regenerator, valves arranged only at the cold ends of the flow paths are adapted to be selectively positioned for allowing the flow paths of each set to be alternately selected, and in which the different sets of flow paths are arranged perpendicularly or at another overlapping desired angle to each other.