When were fridges invented?

Although humans have used various techniques since prehistoric times to keep food cold, the ancestor of the modern refrigerator didn't arrive on the scene until 1748. A demonstration at the University of Glasgow by an inventor by the name of William Cullen is the first known instance of artificial refrigeration.

An American inventor named Oliver Evans designed a refrigeration machine in 1805. In 1834, another inventor, Jacob Perkins, created a refrigerator that used ether to fuel the compression cycle. Until 1929, commercially-produced refrigeration units depended on toxic gases, such as methyl chloride, ammonia and sulfur dioxide, to cool the air. The coolant known as Freon was developed as a result of a collaborative research effort by three separate U.S. companies to find an alternative to these toxic gases. It has since been discovered that Freon poses a significant threat to the ozone layer of the Earth's atmosphere.