Technologies (e.g., devices, systems and methods) for sanitizing reservoirs of humidifiers are described. In some embodiments, the technologies include a sanitization gas system and a connector unit. The connector unit is configured to install into a portion (e.g., wall, bottom, top, or lid) of a reservoir, such as a reservoir of a humidifier. The connector unit includes an inlet passageway for supplying sanitizing gas (e.g., ozone) into the reservoir, and an outlet passageway for removing sanitizing gas from the reservoir. In some embodiments at least a portion of the outlet passageway is disposed radially around the inlet passageway. The sanitization gas system may provide a sanitizing gas to the inlet passageway and receive the sanitizing gas from the outlet passageway.
