"Good ozone" is found in the Mesosphere. Troposphere. Stratosphere. Ionosphere.

The stratosphere or "good ozone" layer extends upward from about 6 to 30 miles and protects life on earth from the sun's harmful ultraviolet (UV) rays. Stratospheric ozone is formed naturally by chemical reactions involving solar ultraviolet radiation (sunlight) and oxygen molecules, which make up 21% of the air we breathe. When ultraviolet radiation strikes an oxygen molecule (O2), it splits the molecule into two separate oxygen atoms (O). These atoms then readily combine with other oxygen molecules to form ozone (O3). This ozone layer then absorbs most of the sun's harmful UV-B radiation. The depletion of the ozone layer is a serious environmental concern, as increased UV radiation can lead to skin cancer, cataracts, and other health problems, as well as damage to plants and ecosystems.