An active humidifier includes a disposable cartridge provided with a humidification chamber adapted to contain water to be heated for air humidification, with an inlet mouth for air introduced by a ventilation device and with an outlet mouth for conditioned air to a patient, the cartridge includes a disposable heating element directly inserted inside the humidification chamber close to the bottom and distanced therefrom, immersed in the water and lapped on all sides, the cartridge also includes an electrical connector for the electrical connection of the disposable heating element, and the disposable heating element includes an electrical resistor and in the humidification chamber is a sealed casing entirely made of plastic material.