Evaporative cooling is a simple, effective and relatively inexpensive approach that can be used in outdoor and indoor environments, but works best in drier, low-to-moderately humid conditions with sufficient airflow. Similar to sweat, evaporative solutions draw heat from your body using an external source of water to create an enhanced cooling effect. More advanced and comfortable than a damp towel, controlled evaporative gear keeps you cool for up to four hours once activated.