Rather than traditional humidification via a chamber filled with water the ResMed AirMini uses atmospheric moisture as well as moisture from your breath to humidify the airflow. This water-less humidification technology is known as heat moisture exchange (HumidX). This form of humidification works via ResMed's HumidX capsules. The ResMed HumidX Plus provides a greater level of humidification compared with the standard ResMed HumidX capsules.