Abstract: An air to air heat exchanger maximizes the space that is available for cooling process air while keeping the pressure drop of the process air through the heat exchanger at a minimum and at the same time utilizes easily available components for manufacture. A pair of headers are provided in the air to air heat exchanger and the headers are connected with a plurality of tubes arranged in a triple tube arrangement such that there are a plurality of sets of three tubes in each set. The sets of tubes are spaced along the length of the headers. Each of the tubes are bent into an "S" shape so each tube has three lengths or sections extending from side to side of the heat exchanger between the input header and output header.