There is a fan in almost every evaporative air coolers that will help draw air outside through the moistened pad; evaporation cools the air as it moves through the pad. The water tank at the coolers have an approximate capacity of approximately 30-40 minutes and the mechanism for heating is a fan. These kinds of coolers have a normal water tank capacity of around of litres and most of them use blowers for cooling purposes. Since air coolers utilize water for the system, they discharge moisture from the air. This approach is based on air delivery or air displacement. Adding moisture to the atmosphere can make rooms feel uncomfortable and muggy.