An adaptor (22) for use in a humidification system (10) for humidifying a flow (D) of pressurized gas to a patient interface device (18). The adaptor includes an inlet (26) structured to be coupled to a supply (12) of pressurized gas, an outlet (28) structured to be coupled to a patient interface device, a port (30) structured to be coupled to an opening of a bottle (24), a first passage (34) extending between the inlet and the port, a second passage (36) extending between the outlet and the port, and a partition disposed generally between the first passage and the second passage proximate the port. The first passage is structured to direct a flow of pressurized gas from the inlet to the port and the second passage is structured to direct a flow of gas from the port to the outlet.
