What is Ozone?

Ozone is a gas that is formed in the atmosphere when three atoms of oxygen combine. Naturally occurring ozone is found high in the stratosphere surrounding the earth and in ground-level ambient air.

Stratospheric Ozone forms high in the atmosphere when intense sunlight causes oxygen molecules (O2) to break up and re-form as ozone molecules (O3). Popularly called "good ozone," it shields people, trees, crops, property, and microorganisms from the harmful effects of the sun's ultraviolet light.

Ground Level Ozone, regularly referred to as “bad ozone” forms when emission sources including, but not limited to, transportation, industrial and commercial operations, and vegetation emit oxides of nitrogen (NOx) and/or volatile organic compounds (VOC) which react in the presence of sunlight.

The Facts About Ozone [TCEQ]

Air Quality Index [EPA]

AirNOW [EPA]

National Ambient Air Quality Standards [EPA]