Abstract: This invention relates to a humidifier which includes a multi-bladed fan which is rotated at a high speed. The blades have flow passages extending therethrough and opening out through their end tips. Liquid is supplied to the center of the fan and distributed to the radiating flow passages. The speed of the blades is such that the liquid is forced through the flow passages in the blade centrifugally so as to produce droplets at the tips of the blade. The droplets are reduced in size by the shear forces of the blade tip passing through the air. The fan maintains the end tip vortex wherein as the droplets appear at the radial ends of the blades, the droplets are drawn rearwardly around the ends of the blades tips and then back through the blades so as to be further reduced in size by shear forces. The rate of fog production is controlled by a flow meter.