Ozone is a gas with a pungent odor and is a main component of smog.
Upper atmospheric ozone acts to shield the earth from the harmful effects of sunlight, and should not be confused with the more dangerous ground-level ozone which is considered a form of air pollution. Electrical sources such as x-ray or ultraviolet generators, arc welding equipment, and mercury vapor lights also produce ozone. Ozone is used as an oxidizing agent in the chemical industry, as a disinfectant for air and water, for bleaching textiles, oils, waxes, and paper pulp, for aging liquor and wood, and in treating industrial waste. Ozone levels in some urban areas typically rise from May through September. Ozone is a respiratory irritant.