Why chlorine destroys stratospheric ozone, how the Montreal Protocol and Title VI of the Clean Air Act turned that science into US law, and the phaseout dates the exam expects you to know.
Notice
Get EPA 608 is an independent study aid. It is not affiliated with, endorsed by, or approved by the U.S. Environmental Protection Agency, the ESCO Institute, Mainstream Engineering, or HVAC Excellence.
Every rule you are about to spend the next few hours learning exists because of one chemical accident of design. The refrigerants that made modern refrigeration cheap and safe were chosen precisely because they are stable — they do not burn, do not corrode, and do not break down. That stability is exactly what makes them a problem. A molecule that will not break down in a compressor will not break down in the lower atmosphere either. It simply drifts.
Understand that sentence and most of Core stops being memorization.
Ozone is O₃ — three oxygen atoms instead of the two in the air you breathe. Most of it sits in the stratosphere, roughly 6 to 30 miles above the surface, in a band thin enough that if you compressed it to sea-level pressure it would be a few millimeters thick.
That thin band absorbs ultraviolet-B radiation. Without it, UV-B reaches the surface at levels that cause skin cancer and cataracts in humans, suppress immune response, damage crop yields, and kill the phytoplankton at the base of the ocean food chain. The exam does not ask you to quantify any of that. It does ask you to know that ozone depletion is a UV-B problem, and that the health effect most often named is skin cancer.
A chlorofluorocarbon released at ground level is not water-soluble, does not react with much of anything, and is not washed out by rain. Over a period of years it mixes upward until it reaches altitudes where solar ultraviolet radiation is intense enough to break it apart. That photolysis frees a chlorine atom.
The chlorine atom then acts as a catalyst. It strips an oxygen atom from an ozone molecule to form chlorine monoxide, that chlorine monoxide reacts with a free oxygen atom, and the chlorine atom is released again — unchanged and ready to repeat. Because it is a catalyst rather than a reactant, a single chlorine atom can destroy on the order of 100,000 ozone molecules before it is finally scavenged into a stable compound.
This is why the halogen content of a refrigerant matters so much:
| Refrigerant family | Contains | Ozone behavior |
|---|---|---|
| CFC (R-11, R-12, R-500, R-502) | Chlorine, fluorine, carbon | Highest ozone depletion; long atmospheric life |
| HCFC (R-22, R-123) | Hydrogen, chlorine, fluorine, carbon | Lower depletion — the hydrogen makes the molecule break down partly in the lower atmosphere |
| HFC (R-134a, R-410A, R-32) | Hydrogen, fluorine, carbon — no chlorine | Zero ozone depletion potential, but significant global warming potential |
| HFO / A2L blends (R-1234yf, R-454B) | Hydrogen, fluorine, carbon with a double bond | Zero ODP and very low GWP; mildly flammable |
Ozone Depletion Potential (ODP) is a ratio, and the reference point is CFC-11, which is defined as 1.0. CFC-12 is also about 1.0. HCFC-22 is roughly 0.05 — about one-twentieth of a CFC — which is exactly why HCFCs were allowed as transitional refrigerants and given a later phaseout date. HFCs have an ODP of zero.
Global Warming Potential (GWP) is a separate ratio measured against carbon dioxide, which is defined as 1. It is not an ozone measure at all, and confusing the two is a classic exam trap. R-134a has zero ODP and a GWP in the region of 1,400. It is harmless to ozone and still tightly regulated — because of the second ratio, not the first.
The Montreal Protocol on Substances that Deplete the Ozone Layer was agreed in 1987 and entered into force on January 1, 1989. It is an international treaty, not a US regulation, and it is the most widely ratified environmental agreement in existence.
The Protocol did not solve the problem at a stroke; it was tightened repeatedly as the science firmed up — London (1990), Copenhagen (1992), Montreal (1997), Beijing (1999), and Kigali (2016). The Kigali Amendment is the one that matters now, because it extends the treaty beyond ozone-depleting substances to the phasedown of HFCs, which deplete no ozone at all but are potent greenhouse gases.
For the exam: Montreal Protocol, 1987, international agreement to phase out ozone-depleting substances.
A treaty has no force inside the United States until Congress implements it. That happened in the Clean Air Act Amendments of 1990, which added Title VI — Stratospheric Ozone Protection. Title VI is the legal home of everything in this course.
The sections you should be able to place:
| Section | Subject |
|---|---|
| 602 | Lists and classifies controlled substances as Class I or Class II |
| 608 | National Recycling and Emission Reduction Program — technician certification, venting prohibition, recovery practices |
| 609 | Motor vehicle air conditioners — a separate certification from 608 |
| 610 | Ban on nonessential products containing ozone depleters |
| 612 | Significant New Alternatives Policy (SNAP) — reviews and approves substitute refrigerants |
Class I substances are the aggressive ozone depleters: CFCs, halons, carbon tetrachloride, methyl chloroform, and methyl bromide. Class II substances are the HCFCs, including R-22 and R-123.
The regulations implementing Section 608 are published at 40 CFR Part 82, Subpart F. Every citation in this course points there.
| Milestone | Date |
|---|---|
| Section 608 venting prohibition takes effect for CFCs and HCFCs | July 1, 1992 |
| US production and import of Class I substances (CFCs) ends | January 1, 1996 |
| Venting prohibition extended to substitute refrigerants such as HFCs | November 15, 1995 |
| HCFC-22 no longer produced or imported for new equipment | January 1, 2010 |
| HCFC-22 production and import ends entirely | January 1, 2020 |
Note what the 1996 and 2020 dates do and do not mean. They ended production and import, not use. Existing R-12 and R-22 equipment stayed legal to operate and to service — it simply had to be serviced with recovered, recycled, or reclaimed refrigerant, or with stockpiled virgin material. That is the entire commercial reason recovery equipment exists, and it is why the recovery rules apply to old refrigerants long after they stopped being manufactured.
Because HFCs have no ODP, Title VI never phased them out. Congress addressed them separately in the American Innovation and Manufacturing (AIM) Act of 2020, which directs EPA to phase down — not out — US production and consumption of listed HFCs by 85% below baseline by 2036, on a stepped schedule. That is a supply restriction, and its practical effect on you is rising prices and the arrival of A2L replacements in new equipment.
Do not let the two programs blur. The venting prohibition, technician certification, and recovery practices you are being tested on come from Section 608. They already apply to HFCs and other non-exempt substitutes, and have done since the mid-1990s for venting and since January 1, 2018 for technician certification and the sales restriction.