It's been thirty years since scientists discovered a hole in the Ozone over Antarctica, a discovery that led to the Montreal Accords that outlawed Freon refrigerants and Halon fire extinguishers (except in submarines and airplanes) and the banning of solvents like carbon tetra-chloride and trichloroethane.
Ozone is a naturally occurring allotrope of Oxygen - a three atom version (O3) as opposed to the two atom O2 we need to sustain life. It has a sharp but not unpleasant odor - it's the smell you notice during a thunderstorm when lightning turns O2 to O3.
Humans have a complex and often confusing relationship with Ozone. Ozone in the stratosphere protects the earth from harmful ultraviolet rays, but more than 0.07 ppm at ground level can lead to respiratory problems and can generate an air quality alert. Meanwhile, folks buy or rent Ozone generators to remove the smells of mold or cigarette smoke from hotel rooms, etc.
It was announced this morning that the hole in the Ozone Layer is the smallest it's been since 1988. Hole watchers, who should be ecstatic, say it is cyclic and normal, or it's the result of Global Warming.