The World We Avoided by Protecting the Ozone Layer Today, September 16, is International Day for the Preservation of the Ozone Layer--the anniversary of the signing of the Montreal Protocol, a landmark piece of legislation that began phasing out the production of ozone-depleting chemicals called chlorofluorocarbons (CFCs). These chemicals, also known by the trade name Freon, were common refrigerants and widely used in aerosol spray cans prior to the Montreal Protocol. In recent years, scientists