EPA 608 Technician Certification Ozone Layer, Refrigerant Types, and Substitutes Summary

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.

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.

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.

HFCs contain hydrogen, fluorine, and carbon but no chlorine, so their ozone depletion potential is zero. Some HFCs still have a high global warming potential, which is why the venting prohibition also covers them.

Wrong choices

• CFCs, such as R-12 and R-11: CFCs have the highest ODP of these groups.
• All halogenated refrigerants: Only refrigerants without chlorine (or bromine) have zero ODP, so not all halogenated refrigerants do.
• HCFCs, such as R-22 and R-123: HCFCs contain chlorine, so their ODP is low but not zero.

The protective ozone layer is in the stratosphere, above the layer where we live and where weather happens. It absorbs much of the sun's harmful ultraviolet (UV) light.

Wrong choices

• The ionosphere: The ionosphere is much higher and is not where the ozone layer is.
• The troposphere: The troposphere is the lowest layer, where weather happens. CFCs drift up through it.
• At ground level: Ozone at ground level is smog, not the protective layer.

CFCs have the highest ODP, HCFCs are lower, and HFCs are zero. ODP is measured against CFC-11, which is set at 1.0.

Wrong choices

• HCFC, then CFC, then HFC: HCFCs have hydrogen, which makes them break down before most of their chlorine reaches the stratosphere, so they rank below CFCs.
• CFC, then HFC, then HCFC: HFCs have zero ODP, so they cannot rank above HCFCs.
• HFC, then HCFC, then CFC: This is the reverse order. HFCs have zero ODP.

When the ozone layer thins, more ultraviolet (UV) radiation reaches the ground. This raises the risk of skin cancer and cataracts, can weaken the immune system, and can harm crops and sea life.

Wrong choices

• Lower oxygen levels in the air we breathe: Ozone depletion does not lower the oxygen we breathe.
• Hearing loss from changes in air pressure: Ozone depletion has nothing to do with hearing.
• More asthma from ground-level smog: Smog is ground-level ozone, a different problem from the ozone layer.

CFCs are very stable, so they do not break down in the lower atmosphere. Over time, winds carry them up to the stratosphere, where strong UV light breaks them apart and frees chlorine.

Wrong choices

• They are lighter than air and float straight up within hours: CFCs are actually heavier than air. They are carried up slowly by air movement over years.
• They react with ground-level smog to form ozone-destroying gas: The damage comes from chlorine released in the stratosphere, not from a reaction with smog.
• They break down quickly in rain and the chlorine rises: CFCs do not break down in rain; they are very stable in the lower atmosphere.

HFCs have zero ozone depletion potential, but many have a high global warming potential (GWP), so they trap heat in the atmosphere. The Section 608 venting prohibition covers non-exempt substitute refrigerants such as HFCs.

Wrong choices

• HFCs are highly toxic to breathe in any amount: Common HFCs have low toxicity; the reason for the rule is climate impact.
• HFCs are always flammable in open air: Most common HFCs used in air conditioning are not highly flammable.
• HFCs turn into CFCs in the atmosphere: HFCs do not change into CFCs.

In some blends (zeotropes), the different refrigerants have different boiling points, so they leak at different rates. The blend left in the system no longer has its original makeup. This is why these blends are charged as a liquid.

Wrong choices

• The blend breaks down into acids when heated: Breaking down from heat is called decomposition, not fractionation.
• The blend separates into oil and refrigerant: Oil separation is a different issue; fractionation is about the refrigerants in the blend.
• The blend freezes into solid pieces in the line: Fractionation has nothing to do with freezing.