Abstract: A water-impervious liner for use in a humidifier having a rotatable drum provided with an evaporator medium and a liquid-holding chamber through which the drum is rotated, said liner being conformed to the shape of the chamber. In one of the embodiments having a single liner, the liner is divided into two chambers by means of a dividing wall having an aperture for the flow of liquid between the chambers. According to an embodiment having a plurality of liners, there is provided a water-impervious liner assembly for use in a humidifier having at least two chambers for holding liquid, wherein the humidifier liner assembly includes a first and a second water-impervious liner and a conduit means interconnecting the two chambers, and the conduit means is attached to the first liner and to the second liner in a watertight manner.