A group of gases – part of the group called HFC gases – that have been used a lot industrially, for example in refrigerators or in firefighting appliances. CFC gases are greenhouse gases and their use is extremely limited today. CFC gases affect the climate but also contribute to depleting the ozone layer, which protects the earth against ultraviolet radiation from the sun. The CFC gases that are already present in the atmosphere are broken down very slowly, and therefore they still contribute to the depletion of the ozone layer and increase the greenhouse effect.