Refrigerator liquefaction. Columns through which gaseous chlorofluorocarbons (CFCs) are converted to liquids. The liquid CFCs can then be destroyed by breaking them down into their chemical constituents. Refrigerators and freezers contain CFCs as coolants (refrigerants) and within polyurethane foam insulation. CFCs are harmful gases that deplete the ozone layer and can trap heat in the atmosphere, which may contribute to the greenhouse effect. Ozone protects life on Earth by blocking the Sun's harmful ultraviolet rays. International agreements have banned production and encouraged destruction of CFCs.