The troposphere generally extends to a level about 6 miles up, where it meets the second layer, the stratosphere. 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.

How does the stratospheric ozone layer form and why is it beneficial? Stratospheric ozone forms and breaks down naturally in a closed-loop cycle. First, UV-C radiation breaks the bonds holding together the oxygen molecule (O2) leaving two free oxygen atoms. Depletion of ozone layer lets UV-B rays reach earth’s surface.

Stratospheric ozone is biologically important because it selectively absorbs much of the incoming solar electromagnetic radiation within the ultraviolet (UV) range. Because ozone selectively absorbs these deleterious wavelengths of solar radiation, it serves as an ultraviolet shield.

The FDA considers medical devices safe if they emit less than 50 ppb of ozone. “The study found that ozone generators, not ionic air purifiers when used appropriately, can generate potentially unsafe levels of ozone indoors,” Stephens says. “None of the Sharper Image air purifiers are ozone generators.”

When an ozone molecule absorbs even low-energy ultraviolet radiation, it splits into an ordinary oxygen molecule and a free oxygen atom.

The stratospheric ozone layer absorbs ultraviolet (UV) radiation, preventing dangerous UV rays from hitting Earth’s surface and harming living organisms. UV rays cannot be seen or felt, but they are very powerful and change the chemical structure of molecules.

Ozone treatment can produce harmful by-products in drinking water. For example, if bromide is present in the raw water, ozone reacts with it to form bromate, shown to cause cancer in rats.