Method and apparatus for dehumidification

A dehumidifier (1) comprises a housing (2) provided with a process air inlet (3) and a process air outlet (4) and a drying device (6) provided with moisture adsorption means. A fan (10) adapted to bring process air entering through the process air inlet (3) to pass the drying device (6) and, subsequent to having been dehumidified, depart through the process air outlet (4). Means (12) for heating regeneration air passing through the drying device (6) for regeneration of the moisture adsorption means and then passing to a regeneration air outlet (21) are also provided. By providing a heat-exchanger (8) with a first inlet connected and a second inlet for effecting an exchange of heat between air entering through the first inlet and air entering through the second inlet; and a valve (20) switchable between a first position, allowing wet regeneration air to exit through the regeneration air outlet; and a second position, allowing an exchange of heat between wet regeneration air having passed through the drying device (6) and air entered through the first inlet of the heat-exchanger, a dual operation mode dehumidifier is obtained. A method for drying air is also provided.