A surgical humidification system includes a source of gas flow and a humidifier that receives the gas flow and outputs a humidified gas to a delivery conduit. The delivery conduit has an outlet and a suitable interface, such as a diffuser, is connected to the outlet. The interface can be positioned near or within an open surgical cavity of a patient to supply the humidified gas to the cavity. The system also includes a pressure relief arrangement that operates to relieve pressure from the system above a normal operating pressure. The pressure relief arrangement can be located in a non-sterile portion of the system, such as upstream from the humidifier, for example.