Abstract: In some embodiments, a humidification system includes a heater base having a heater plate, a humidification chamber, and circuit. The circuit can include various conduits, including an inspiratory conduit, expiratory conduit, Y-piece, patient conduit, and/or dry conduit. In use, the chamber contains a quantity of liquid. The heater base heats the heater plate, which in turn heats the liquid to a temperature that causes at least some of the liquid to become vapor, thereby humidifying the gases within the chamber. The gas is delivered to the patient via the inspiratory conduit. Various features can help control the system and ensure the patient receives gases having the desired conditions. These features can be used individually or in various combinations and subcombinations both in existing humidification systems and improved systems for respiratory humidification, laparoscopy, and other purposes.