Pure ozone is a blue gas with a unique odor.
Ozone occurs naturally and is present in the ozone layer of the air. Ozone in the lower atmosphere is a pollutant that can damage the lungs. It is produced when an electric discharge, such as lightning, passes through the air or as a product of auto exhaust. Onset of severe symptoms after the exposure to ozone can be delayed. Those symptoms can include headache, upset stomach or vomiting, pain or tightness of the chest, shortness of breath or tiredness.