Ozone depletion
Short answer · Updated 2026
Ozone depletion is the thinning of the stratospheric ozone layer caused by chlorine (and bromine) from man-made chemicals. CFC refrigerants such as R-12 have an ozone depletion potential of about 1.0, R-22 is 0.055, and HFCs are zero because they contain no chlorine. It is the original reason venting refrigerant is prohibited.
Ozone depletion is the thinning of the ozone layer in the stratosphere, the region of the upper atmosphere where ozone absorbs much of the sun's harmful ultraviolet radiation before it reaches the surface. Less ozone overhead means more ultraviolet exposure at ground level, with consequences that include increased skin cancer risk, eye damage, and harm to crops and marine life. Protecting this layer is a global concern because the atmosphere does not respect borders.
Refrigerants enter the story through chlorine. When chlorine bearing refrigerant molecules escape and migrate to the stratosphere, ultraviolet light liberates their chlorine atoms, and each freed atom can destroy ozone molecules repeatedly through catalytic reactions. A small mass of released refrigerant can therefore do disproportionate damage, which is why the venting of regulated refrigerants was prohibited rather than merely discouraged.
Section 608 is, at its root, ozone protection law. The certification exam expects candidates to connect the chemistry to the obligations: which refrigerant families carry chlorine, why their release matters, and how recovery, recycling, and reclamation exist to keep those compounds inside equipment and out of the sky. Understanding ozone depletion turns the rules from arbitrary requirements into a coherent response to a documented harm.
Common questions
What is the definition of ozone layer depletion?
Ozone layer depletion is the thinning of the ozone layer in the stratosphere, where ozone absorbs much of the sun's ultraviolet radiation. The thinning comes from chlorine and bromine released by man-made chemicals.
What depletes the ozone layer?
Chlorine-bearing chemicals, mainly CFCs and HCFCs. Ultraviolet light in the stratosphere frees their chlorine atoms, and each atom can destroy many ozone molecules in catalytic reactions.
What does zero ozone depletion potential mean?
It means the refrigerant contains no chlorine or bromine, so it cannot destroy stratospheric ozone. HFCs such as R-134a and R-410A have an ODP of zero, although many still have a high global warming potential.
How does ozone depletion connect to Section 608?
Section 608 of the Clean Air Act is ozone protection law. The venting prohibition, recovery requirements and technician certification all exist to keep chlorine-bearing refrigerant inside equipment and out of the stratosphere.
Sources
- Ozone depletion potentials: Montreal Protocol on Substances that Deplete the Ozone Layer, Annexes A and C.
- US program: EPA Stratospheric Protection program under Clean Air Act Title VI (40 CFR Part 82).
Related terms
| CFC (chlorofluorocarbon) | An early family of refrigerants containing chlorine, fluorine, and carbon, with severe ozone depletion effects. |
| HCFC (hydrochlorofluorocarbon) | A transitional refrigerant family that added hydrogen to reduce, but not eliminate, ozone depletion. |
| Global warming potential (GWP) | A measure of how much heat a substance traps in the atmosphere relative to carbon dioxide. |
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