When there is lack of fresh air in an air-conditioned environment,it will cause the deterioration of the indoor air quality,this may lead to "air condition syndromes",It's common to decrease the fresh air volume in order to reduce the energy consumption and limit the cooling capacity.The increase of fresh air means the increase of cooling capacity and also it means the increase in bill.Using Jetex-Lloyd's rotary heat exchanger unit or plate heat exchanger can get you out of this predicament.