Ozone (O3)

Ozone is a highly reactive gas with three oxygen atoms. It is a pale blue gas with a distinctively pungent, irritating smell resembling chlorine bleach, also can be detectable at 0.1 ppm concentrations in the air. Also, being a powerful oxidizing agent, it is highly combustible at 10 wt% or higher concentrations. Also, it is highly unstable and hence gets converted to O2 at high concentrations.