A bypass adaptor for a respiratory assistance system including an inlet connector configured to connect to a gases source outlet and defining a first gases passageway with a first axis and an outlet connector configured to connect to an inspiratory conduit connector and defining a second gases passageway with a second axis, the second gases passageway being fluidly connected to the first gases passageway, the inspiratory conduit connector being incompatible with direct connection to the gases source outlet, wherein the first axis is separated from the second axis by an angle that allows the inspiratory conduit connector to be connected via the bypass adaptor to the gases source outlet in a space smaller than the length of the inspiratory conduit connector. Also provided are a port cap assembly and a humidifying apparatus including the port cap assembly, wherein the port cap assembly provides for improved assembly and/or usability.