A humidification system can include a heater base, a chamber, and a breathing circuit. The heater base includes a heater plate positioned in a recessed region, and a heat conductive portion of the chamber is configured to contact the heater plate. The heater base includes a guard configured to control movement of the chamber into and out of the recessed region. The guard includes an anti-racking mechanism. The chamber includes an inlet port, an outlet port. A downward extension extends into the chamber from the inlet port, and a baffle is disposed at a lower end of the downward extension. A component of the breathing circuit can include a conduit hanging end cap for shipping and storage. The end cap can include a hanging component to allow the breathing circuit component to be hung from a medical stand. The system can detect when breathing circuits are connected in reverse.