Ozone, a molecule composed of three oxygen atoms (O3), is a pale blue gas with a distinctive, sharp scent that is often described as crisp, clean, and somewhat similar to the smell of chlorine. This scent is most notably detected after thunderstorms, which is due to lightning discharges that naturally produce ozone by splitting oxygen molecules in the air. The resulting scent contributes to the fresh and invigorating quality of the air following a storm. Ozone's odor is also detectable in photocopiers and electric motors, as these devices can generate small amounts of ozone during operation. In terms of its odor profile, ozone is considered to have a metallic quality, with a somewhat pungent smell that can become unpleasant and irritating at higher concentrations. It is used in various applications for its oxidizing properties, including water purification and air cleaning, though its levels must be carefully controlled due to potential health risks associated with prolonged exposure.