Trichlorofluoromethane, also called freon-11, CFC-11, or R-11,  is a chlorofluorocarbon (CFC).  It is a colorless, faintly ethereal, and sweetish-smelling liquid that boils around room temperature.  CFC-11 is a Class 1 ozone-depleting substance which allegedly damages Earth's protective stratospheric ozone layer.