In today's conditions, the importance of heat recovery has increased due to the increase in energy costs. In air handling units operating with mixed air or 100% fresh air, high energy savings are achieved by heating or cooling the fresh air a little by making use of the exhaust air thrown out. For this purpose, Klisom Air Handling Units offer air-to-air or water-to-air heat recovery options. In water-to-air heat recovery air handling units, a Copper pipe/Aluminum finned coil is used for heating conditions, on the exhaust side to take the energy from the indoor air, and on the fresh air side to transfer the energy obtained by the exhaust to the fresh air. A pump is used to provide water circulation between the two batteries. In cooling conditions, the operation sequence is reversed. In air-to-air heat recovery systems, the energy transfer is made from the exhaust air to the fresh air (provided that it is the reverse in cooling conditions). In 100% fresh air devices, as in normal conditions, instead of double body manufacturing, one size device including the heat recovery unit is manufactured. Device designs can be different depending on the project and indoor-outdoor weather conditions.