An apparatus or kit for a respiratory support system for delivering humidified gas to a user or patient. The apparatus comprising a humidifier chamber in pneumatic communication with a gases source, an inspiratory conduit in pneumatic communication with the humidifier chamber downstream of the humidifier chamber, a filter that is in pneumatic communication with the inspiratory conduit downstream of the inspiratory conduit, and a patient interface for delivering humidified gas to a user or patient, wherein the patient interface is in pneumatic communication with the filter downstream of the filter, or is configured to be placed in pneumatic communication with the filter downstream of the filter.