An electronic display comprising a housing and, disposed within the housing : an electronic display panel having a display face visible from outside the housing ; a heat-exchanger arranged to exchange heat between internal and external fluids without direct contact between the internal and external fluids, the internal fluid circulating within the housing and the external fluid being received from externally of the housing and output to externally of the housing ; a heat source ; impellers for impelling said fluids through the heat-exchanger ; a controller for controlling the heat source and the flow of fluids through the heat-exchanger ; temperature sensing means (300-310); and humidity sensing means (301-311): wherein the internal fluid is air and the controller is arranged, in use, to: receive temperature and humidity data from the temperature and humidity sensing means (300-311); process the received temperature and humidity data to indicate a current dew point within the housing ; compare the current dew point with a current location temperature at or adjacent the heat-exchanger ; and if the current location temperature is at or below the current dew point, control the flow of fluids through the heat-exchanger to raise the temperature at at least one location on the heat-exchanger and/or activate the heat source to raise the temperature within the housing . an electronic display panel having a display face visible from outside the housing ; a heat-exchanger arranged to exchange heat between internal and external fluids without direct contact between the internal and external fluids, the internal fluid circulating within the housing and the external fluid being received from externally of the housing and output to externally of the housing ; a heat source ; impellers for impelling said fluids through the heat-exchanger ; a controller for controlling the heat source and the flow of fluids through the heat-exchanger ; temperature sensing means (300-310); and humidity sensing means (301-311): wherein the internal fluid is air and the controller is arranged, in use, to: receive temperature and humidity data from the temperature and humidity sensing means (300-311); process the received temperature and humidity data to indicate a current dew point within the housing ; compare the current dew point with a current location temperature at or adjacent the heat-exchanger ; and if the current location temperature is at or below the current dew point, control the flow of fluids through the heat-exchanger to raise the temperature at at least one location on the heat-exchanger and/or activate the heat source to raise the temperature within the housing . wherein the internal fluid is air and the controller is arranged, in use, to: receive temperature and humidity data from the temperature and humidity sensing means (300-311); process the received temperature and humidity data to indicate a current dew point within the housing ; compare the current dew point with a current location temperature at or adjacent the heat-exchanger ; and if the current location temperature is at or below the current dew point, control the flow of fluids through the heat-exchanger to raise the temperature at at least one location on the heat-exchanger and/or activate the heat source to raise the temperature within the housing . receive temperature and humidity data from the temperature and humidity sensing means (300-311); process the received temperature and humidity data to indicate a current dew point within the housing ; compare the current dew point with a current location temperature at or adjacent the heat-exchanger ; and if the current location temperature is at or below the current dew point, control the flow of fluids through the heat-exchanger to raise the temperature at at least one location on the heat-exchanger and/or activate the heat source to raise the temperature within the housing . <EOS>