CFC-11, also known as trichlorofluoromethane, is a type of chlorofluorocarbon (CFC) that was commonly used as a refrigerant and in foam production. It is a colorless gas at room temperature and has been linked to ozone layer depletion, which protects the Earth from harmful ultraviolet radiation. Due to its environmental impact, the production and use of CFC-11 were largely phased out under the Montreal Protocol, an international treaty established in 1987. This agreement aimed to reduce substances that harm the ozone layer, leading to a significant decrease in CFC-11 emissions and helping to promote a healthier atmosphere.