Atmosphere The lowest layer is the troposphere, which extends from the surface to the bottom of the stratosphere. Three quarters of the atmosphere's mass resides within the troposphere, and is the layer within which the Earth's terrestrial weather develops. The depth of this layer varies between 17 km at the equator to 7 km at the poles. The stratosphere, extending from the top of the troposphere to the bottom of the mesosphere, contains the ozone layer. The ozone layer ranges in altitude between 15 and 35 km, and is where most of the ultraviolet radiation from the Sun is absorbed. The
Ozone monitor Ozone monitor An ozone monitor is electronic equipment that monitors for ozone concentrations in the air. The instrument may be used to monitor ozone values for industrial applications or to determine the amount of ambient ozone at ground level and determine whether these values violate National Ambient Air Quality Standards (NAAQS). The ozone molecule absorbs ultraviolet radiation, and most ozone monitors utilized in regulatory applications use ultraviolet absorption to accurately quantify ozone levels. An ozone monitor of this type operates by pulling an air sample from the atmosphere into the machine with an air pump. During one cycle, the ozone