The invention relates to a continuous gas separation method which makes use of pressure differences, and to the use of this method in ventilation technology. According to the invention, a diaphragm is located in the main stream and gas separation takes place in parallel by means of pressure differences. The invention provides a means of dehumidifying the air without cooling the air. This reduces the energy consumed to one third of that used by a dewpoint-regulated air-conditioning system and to half of that consumed by partial dehumidification with low surface temperatures, without using chlorofluorocarbon or fluorocarbon systems.