A humidification system for delivering humidified gases to a user can include a heater base, humidification chamber having an inlet, outlet, and associated fluid conduit, and breathing circuit including a supply conduit, inspiratory conduit, and optional expiratory conduit. The humidification system can include various features to help make set-up less difficult and time-consuming. For example, the supply conduit, inspiratory conduit, and optional expiratory conduit can be coupled into a one-piece circuit to aid set-up. Various components can be color-coded and can have corresponding structures to indicate which components should be connected to one another during set-up. Such features can also help make the set-up process more intuitive for an operator, which can reduce the need for specialized training and reduce the number of potential errors.