Ozone is a form of oxygen with three atoms, instead of the usual two atoms.
It is a photochemical oxidant and, at ground level, is the main component of smog. These gaseous compounds mix like a thin soup in the ambient, or outdoor, air, and when they interact with sunlight, ozone is formed. Sources of these pollutants include automobiles, gas-powered motors, refineries, chemical manufacturing plants, solvents used in dry cleaners and paint shops, and wherever natural gas, gasoline, diesel fuel, kerosene, and oil are combusted. Ozone pollution is the periodic increase in the concentration of ozone in the ambient air, the natural air that surrounds us. It is mainly a daytime problem during summer months because warm temperatures play a role in its formation.