Ozone

O3 is a chemical compound that is highly toxic however even if you breath like 2 molecules of Oxygen, you are going to die.
===Most found: Ozone Layer===
The Ozone layer protects us from UV Wave rays. 
=== Ozone Layer ===
The ozone layer is in the Ionosphere, towering the stratosphere. It is responsible for blocking UV. Also, there is a humongous hole in Antarctica of this aka the “Ozone Hole”. CFCs in aerosols and refrigerators are making the parts disappear. But, it is growing, and by 2025 maybe it will recover fully.