Humidifier reservoir

Disclosed is a water reservoir for humidifying a flow of breathable gas generated by an RPT or CPAP apparatus that reduces cost of production while retaining heat transfer performance. The water reservoir is configured for being removably received by a water reservoir dock of the apparatus, the water reservoir dock having a heater plate. The water reservoir has a reservoir base including a cavity structured to hold a volume of liquid, the reservoir base including a hole; and a conductive portion provided to the reservoir base, the conductive portion including a film comprising a non-metallic material and arranged to thermally engage with the heater plate to allow transfer of heat from the heater plate to the volume of liquid in use. The film is secured so that the film seals the hole and perimeter edges of the film extend beyond edges of the hole. The thin film is formed from a silicone elastomeric material, has a wall thickness less than about 0.5 mm, and is generally planar with one or more ribs structured and arranged to extend across the film.