Abstract: A humidifier includes a reservoir for containing water and a steam generator incorporating an electrical heater for turning the water into steam. The generator includes an upwardly extending passage having a lower end for the entrance of steam produced by the heater into the passage and an upper end for exit of the steam. A freely rotatable fan is located in the passage for turning by the steam rising through the passage. An opening is located at the passage lower end, below the fan, for intake of relatively drier air from outside for mixing with rising steam to produce moderately moisturised air.