Human: I've been hearing a lot about the "ozone hole." What's that? Assistant: 
The ozone layer is a thin layer of gas in the stratosphere that protects us from ultraviolet radiation. It’s made up of three main components: Ozone, nitrogen dioxide, and carbon dioxide. The ozone layer absorbs most of the harmful UVB rays from the sun, but it can be destroyed by certain chemicals called “chlorofluorocarbons” (CFCs). These chemicals were widely used in aerosol sprays, refrigeration systems, and air conditioners until they were banned in 1987 because they were destroying the ozone layer.