A humidifier assembly for a CPAP apparatus includes a liquid storage container configured to hold a body of liquid. The liquid storage container includes a humidifying region above a metallic heat conducting material, the humidifying region being a region inside the liquid storage container in which the liquid is evaporated into pressurized respiratory gas generated in the CPAP apparatus. The CPAP apparatus also includes a base unit configured to a) receive the liquid storage container and b) securely and releasably connect to a CPAP unit of the CPAP apparatus, the base unit having a bottom portion to support the liquid storage container thereon, the bottom portion including a heating element configured to contact the heat conducting material of the liquid storage container when the liquid storage container is supported on the base unit. When the liquid storage container is received by the base unit, the liquid storage container and the base unit together define an airflow path through the humidifier assembly, an inlet of the airflow path being upstream of the liquid storage container and an outlet of the airflow path being downstream of the liquid storage container.