Abstract: A humidifier for use in forced air heating systems is provided wherein a housing having a water reservoir therein is adapted to be positioned adjacent an air register, outlet or diffuser. A duct in communication with said air register is provided within the housing for delivery of air to the water reservoir, and a flexible curtain or baffle is positioned within the housing across said duct and extending into the water of said reservoir. This arrangement requires the forced air entering said duct to flex, balloon or bow out the curtain to raise it above the water surface in order to escape to the outside. The device is adaptable to forced air floor, wall or overhead registers, outlets or diffusers.