A humidifier (68, 68′, 100, 100′) for an airway pressure support system (50), includes a base (70, 102), a number of side walls (76, 78, 104) extending from the base, and a top wall (80, 106) provided opposite the base, wherein the base, the number of side walls, and the top wall are made form an elastomeric material and at least partially define an internal chamber (82) for receiving and holding a liquid. The humidifier also includes a plurality of support structures (88, 88′, 112, 114, 118, 120) provided on or within the humidifier, each support structure extending along at least the number of side walls, wherein the humidifier is structured to collapse from an initial, expanded condition to a collapsed condition when a compressive force is applied to the top wall in the initial, expanded condition and to automatically return to the initial, expanded condition when the force is removed.
