Ozone is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope O2, breaking down in the lower atmosphere to O2 or dioxygen. Ozone is formed from dioxygen by the action of ultraviolet light and also atmospheric electrical corona discharges. Ozone occurs quite readily in nature, most often as a result of lightning strikes that occur during thunderstorms. In fact the “fresh, clean, spring rain” smell that we notice after a storm most often results from nature’s creation of ozone. However, we are probably most familiar with ozone from reading about the “ozone layer” that circles the planet above the earth’s atmosphere. This ozone serves to protect us from the ultra-violet radiation.
Ozone’s odour is sharp, reminiscent of chlorine, and detectable by many people at concentrations of as little as 10 ppb in air. In standard conditions, ozone is a pale blue gas that condenses at progressively cryogenic temperatures to a dark blue liquid and finally a violet-black solid. Ozone’s instability with regard to more common dioxygen is such that both concentrated gas and liquid ozone may decompose explosively at elevated temperatures or fast warming to the boiling point. It is therefore used commercially only in low concentrations.
Ozone is the second most powerful sterilant in the world and can be used to destroy bacteria, viruses and odors which has many industrial and consumer applications related to oxidation such as medical treatment, water purification and air cleaning, Etc.