Humidifier and layered heating element

A respiratory apparatus for providing a pressurized flow of breathable gas for respiratory therapy of a patient, including a flow generator to supply the pressurized flow of breathable gas and a humidifier to humidify the pressurized flow of breathable gas. The humidifier includes a gas inlet configured to receive the pressurized flow of breathable gas from the flow generator, a tub (460) adapted to hold a liquid, the tub including sidewalls and a bottom, a gas outlet adapted to be connectable to a tube to provide humidified gas to a patient interface and a heating apparatus. The heating apparatus includes a heating element (474) which converts electrical power to heat energy, a thermally conductive hot plate (470) having a first surface and a second surface, the first surface of the hot plate being arranged to receive the heat energy from the heating element, the second surface of the hot plate being configured and arranged to heat the liquid in the tub and a protective coating (469) overmolded over the hot plate to provide a sealed protective layer across the second surface of the hot plate. The protective coating provides a water and/or vapor sealed protection layer across the heating surface.