EPA 608 Technician Certification: Ozone Layer, Refrigerant Types, and Substitutes Concepts
Importance ★★★★★ · 25% (estimate)
Overview
This chapter explains why EPA controls refrigerants at all. You will learn how some refrigerants damage the ozone layer, how to tell the three main refrigerant families apart, and why non-exempt substitute refrigerants such as HFCs still may not be vented. It also covers what to expect when a system is changed to a substitute refrigerant.
The ozone layer sits in the stratosphere and blocks much of the sun's ultraviolet (UV) light. CFCs and HCFCs are stable enough to drift up there, where strong UV light breaks them apart and frees chlorine. One chlorine atom can destroy many ozone molecules. Less ozone means more UV at ground level, which raises the risk of skin cancer and cataracts.
CFCs such as R-12 and R-11 contain chlorine and no hydrogen, so they have the highest ozone depletion potential (ODP). HCFCs such as R-22 and R-123 contain hydrogen too, so their ODP is lower. HFCs such as R-134a and R-410A contain no chlorine and have zero ODP, but many have a high global warming potential (GWP).
There is no true drop-in replacement for an older refrigerant. A retrofit may need a different oil, such as ester (POE) oil for HFCs instead of mineral or alkylbenzene oil. Some blends fractionate, which means their parts leak at different rates, so they are charged as a liquid.
Key concepts
CFC
Chlorofluorocarbon: a refrigerant made of chlorine, fluorine, and carbon, such as R-11 and R-12. It has the highest ozone depletion potential.
Memory tipC-F-C: chlorine, no hydrogen. R-12 and R-11.
HCFC
Hydrochlorofluorocarbon: a refrigerant that contains hydrogen as well as chlorine, such as R-22 and R-123. It depletes ozone less than a CFC but still depletes it.
Memory tipThe H means it breaks down sooner. R-22, R-123.
HFC
Hydrofluorocarbon: a refrigerant with no chlorine, such as R-134a and R-410A. Its ozone depletion potential is zero, but many HFCs have a high global warming potential.
Memory tipNo chlorine, no ozone harm, but still no venting.
Ozone depletion potential (ODP)
A number comparing a chemical's harm to ozone with the harm from the same mass of CFC-11, which is set at 1.0.
Memory tipOrder: CFC > HCFC > HFC (zero).
Fractionation
When the refrigerants in a blend leak or boil off at different rates, so the blend left behind no longer has its original makeup.
Memory tipFractionating blends: charge as a liquid.
Ester (POE) oil
A synthetic oil commonly used with HFC refrigerants such as R-134a. Older CFC and HCFC systems often use mineral or alkylbenzene oil.
Memory tipHFC = ester oil; HCFC = often alkylbenzene.
Source: EPA Section 608 Test Topics · as of 2025
Often tested
- Chlorine is the ozone-destroying part of CFCs and HCFCs.
- The ozone layer is in the stratosphere.
- HFCs have zero ODP, but venting them is still illegal under 40 CFR 82.154(a). Many also have a high GWP.
- There is no true drop-in substitute; retrofits may need an oil change.
- Charge zeotropic (fractionating) blends as a liquid.
Easy to confuse: Refrigerant families
| Family | Contains chlorine? | Ozone depletion | Examples |
|---|---|---|---|
| CFC | Yes | Highest | R-11, R-12 |
| HCFC | Yes | Lower | R-22, R-123 |
| HFC | No | Zero | R-134a, R-410A |
3 sample questions
Verified practice questions from this unit.
Question 1. Which element in CFC and HCFC refrigerants destroys ozone in the stratosphere?
- ① Fluorine
- ② Chlorine
- ③ Carbon
- ④ Hydrogen
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Answer: ② Chlorine
Key point: Chlorine in CFCs and HCFCs destroys ozone
Strong sunlight high in the stratosphere breaks CFC and HCFC molecules apart and frees chlorine atoms. Each chlorine atom then breaks down ozone molecules. HFCs contain no chlorine, so they do not harm the ozone layer.
Wrong choices
- Fluorine: Fluorine is in CFCs, HCFCs, and HFCs, but it is not what breaks down ozone in these refrigerants.
- Carbon: Carbon is the backbone of the molecule and does not destroy ozone.
- Hydrogen: Hydrogen actually makes HCFCs break down sooner in the lower atmosphere, so less chlorine reaches the ozone layer.
Question 2. R-12 belongs to which group of refrigerants?
- ① HFC (hydrofluorocarbon)
- ② HFO (hydrofluoroolefin)
- ③ HCFC (hydrochlorofluorocarbon)
- ④ CFC (chlorofluorocarbon)
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Answer: ④ CFC (chlorofluorocarbon)
Key point: R-12 and R-11 are CFCs
R-12 is a CFC: it is made of chlorine, fluorine, and carbon with no hydrogen. Other common CFCs are R-11, R-113, R-114, and R-115. CFCs have the highest ozone depletion potential of the refrigerant groups.
Wrong choices
- HFC (hydrofluorocarbon): HFCs such as R-134a contain no chlorine. R-12 does contain chlorine.
- HFO (hydrofluoroolefin): HFOs such as R-1234yf are newer low-GWP refrigerants, not R-12.
- HCFC (hydrochlorofluorocarbon): HCFCs contain hydrogen; R-22 and R-123 are examples, not R-12.
Question 3. R-22 belongs to which group of refrigerants?
- ① HCFC (hydrochlorofluorocarbon)
- ② HFC (hydrofluorocarbon)
- ③ Hydrocarbon
- ④ CFC (chlorofluorocarbon)
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Answer: ① HCFC (hydrochlorofluorocarbon)
Key point: R-22 and R-123 are HCFCs
R-22 is an HCFC. It contains hydrogen, chlorine, fluorine, and carbon. Because of the hydrogen, it breaks down faster in the lower atmosphere than a CFC, so it harms ozone less, but it still depletes ozone. R-123 is another common HCFC.
Wrong choices
- HFC (hydrofluorocarbon): HFCs contain no chlorine. R-22 contains chlorine.
- Hydrocarbon: Hydrocarbons such as propane (R-290) contain only hydrogen and carbon.
- CFC (chlorofluorocarbon): CFCs have no hydrogen. R-22 contains hydrogen, so it is an HCFC, not a CFC.
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