Technologies (e.g., devices, systems and methods) for sanitizing mist 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 an opening in the mist humidifier that is used in operation to release mist for humidification purposes. The connector unit includes an inlet passageway for supplying sanitizing gas (e.g., ozone) into the humidifier, and an exhaust system for removing sanitizing gas from the reservoir.