![Print Print](https://www.e-education.psu.edu/rocco/sites/all/modules/print/icons/print_icon.png)
Ozone (O3) is a triatomic oxygen molecule gas that occurs both in the Earth’s upper atmosphere and at ground level. Ozone can be good or bad, depending on where it is found: It is a bluish gas that is harmful to breathe. Therefore, it is bad at the ground level.