Air conditioners make air cooler by circulating it through a freon mechanism, similar to what happens in a refrigerator. They are functionally different from fans, because fans don't actually cool air, but only make it feel cooler by moving it around. The advantage of air conditioners is that they increase comfort levels during hot weather, but they can also present various disadvantages.
Most people use air conditioners to stay more comfortable in their homes or offices during hot and humid summer weather. Under extreme conditions, air conditioners may keep elderly and other vulnerable people safer from heat-induced health problems. Air conditioners are used in many commercial settings not only for increased comfort but for decreasing heat stress on delicate machinery such as computers, and reducing food spoilage in grocery stores and restaurants.
Air conditioners use a lot of electricity. This creates both financial disadvantages for the people who have to pay for the power, and more generalised environmental disadvantages caused by power production. Because a large percentage of electricity is created by coal-burning power plants, air conditioning contributes indirectly to the release of greenhouse gases and other pollutants. In addition, according to The Independent, spending too much time in an air-conditioned environment can contribute to health problems such as asthma, tightness in the chest and other respiratory ailments.
In poorly designed buildings, air-conditioning is sometimes used to make up for poor design and lack of insulation. Well-designed buildings can orient themselves to the sun in a way that reduces summer heat gain, using shade trees and insulation to reduce the effect of high temperatures on the interior climate. Even when air conditioners are being used, these measures will reduce their workload, decreasing their power usage and increasing their lifetimes. The advantages of air conditioners can, therefore, be maximised when used in conjunction with environmentally sound design and common sense.