A humidifier includes a humidifier tub with an air inlet and an air outlet. An uppermost end of the air outlet terminates at an exit port positioned in a plane disposed below the air inlet. The air inlet is configured so that air enters the humidifier tub through the air inlet in a lateral direction. The humidifier also includes a base plate provided to a bottom of the humidifier tub. The base plate and humidifier tub define a water chamber adapted to receive a volume of liquid water. The humidifier tub further includes a guidance structure adapted to direct air entering the humidifier tub via the air inlet to swirl downwardly and around within the water chamber and into contact with the liquid water before exiting the exit port.