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Sealed System
HCFCs
Hydrochlorofluorocarbons (HCFCs) are compounds comprised of hydrogen, chlorine, fluorine, and carbon atoms.
These compounds have many of the useful properties of CFCs, but are destroyed naturally in the lower atmosphere
and do not persist to the same extent as CFCs. Only a fraction of HCFCs emitted can be transported to the ozone
layer in the stratosphere where their chlorine could deplete ozone. HCFCs typically have an ozone depletion
potential 2 to 10 percent that of CFCs.
HFCs
Hydrofluorocarbons (HFCs) are compounds consisting of hydrogen, fluorine, and carbon atoms which, like the
HCFCs, are destroyed naturally in the lower atmosphere. They have many of the useful properties of the CFCs.
Because they do not contain chlorine, they are not involved in ozone depletion.
NOT-IN-KIND (NIK) Technologies
Technologies that do not rely on the use of fluorocarbons.
Ozone
Ozone, formed in the stratosphere by the action of sunlight on oxygen, is also an airborne pollutant near ground
level. Low altitude (tropospheric) ozone is formed by reactions between hydrocarbons and oxides of nitrogen in
sunlight.
Ozone Depletion
Ozone is continually being formed and destroyed by chemical reactions occurring in the stratosphere. There are
large natural changes in ozone concentration in the stratosphere; for example, between summer and winter there is
a change of about 25 percent at mid-latitudes. Ozone depletion occurs if the rate of ozone destruction is increased
due to human activities.
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