Atmosphere

The atmosphere is a very loose amalgamation of all gases that surround the earth due to gravity.
Knowing that, O3 has gathered in the atmosphere, protecting the earth from the sun's UV lights, which otherwise would destroy our planets and heighten our chances of cancer.
The ozone-layer existing didn't seem to have saved the nutjob though.
That aside in the last couple decades, humans have been damaging the ozone-layer by spoiling it with chemicals. Only recently after many years of regulations on CFCs and refrigrants has the ozone layer started recovering, meaning it's still weak.