Where Is the Ozone

UV-C 200-280 nm Most energetic Completely absorbed by oxygen and/or ozone in the atmosphere may cause significant biological damage. 

In the absence of anthropogenic influences, the concentration of ozone in the stratospheric ozone layer had maintained a steady state (a state in which the net rate of destruction equals the net rate of formation) for millions of years. On the average, ozone molecules were destroyed by a variety 

Steady state A state in which the concentration of a chemical remains essentially constant even though the chemical may be undergoing numerous chemical reactions 

We can illustrate a steady state condition by using a bathtub analogy. A bathtub is filled to a certain level with water, and then the drain is opened. One can maintain a constant level of water in the tub, even with an open drain, by carefully adding water to the tub with the faucet at exactly the rate at which it is draining away. 

A slightly simplified version of the steady-state process for ozone formation (reactions 1 and 2) and destruction (reactions 3 and 4) is known as the Chapman cycle (shown in left margin) after the scientist who proposed it. 

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