The thickness of ozone in a column of air in the atmosphere is measured in terms of:

Step-by-step solution

Most atmospheric ozone is concentrated in a layer in the stratosphere. The Dobson Unit is a way to describe how much ozone there would be in the column if it were all squeezed into a single layer. The average amount of ozone in the atmosphere is roughly 300 Dobson Units, equivalent to a layer 3 millimetres (0.12 inches) thick.