If an indoor installation of TTR 400 D or TTR 500 D is not permitted, undesirable due to the noise or impossible to realize for other reasons, e.g. in accommodation or storage facilities, the Drybox enables their weatherproof outdoor installation. Developed especially for the professional circulating air drying on dew point level using these two desiccant dehumidifiers, the Drybox comes with suitable openings for hose connection as well as with a service flap for the device configuration.