11.3 - Refrigerant Family and Environmental Comparison

Module: Standalone Reference Appendices and Instructor Resources
Purpose: Consolidated family-level reference for refrigerant composition, ozone impact, climate impact, typical applications, pure/blend behavior, and major service cautions
Project integration review date: August 14, 2026
Regulatory/scientific verification basis: Current project Modules 2–3 plus current EPA ozone-protection, HFC/AIM Act, SNAP, and refrigerant-safety information
Scope note: This file compares refrigerant families. Detailed refrigerant-by-refrigerant lookup information is reserved for 11.17 - Common Refrigerant Quick Reference.md.

How to Use This Reference

Use this file when you need to answer questions such as:

• Is this refrigerant a CFC, HCFC, HFC, HFO, hydrocarbon, or natural refrigerant?
• Does the family contain chlorine?
• Does the family have ozone-depletion potential?
• Does zero ODP also mean low climate impact?
• Is the refrigerant normally a pure fluid or a blend?
• What applications are commonly associated with the family?
• What major service or safety issue should be remembered first?

For rapid identification:

CFC
→ carbon + chlorine + fluorine

HCFC
→ hydrogen + carbon + chlorine + fluorine

HFC
→ hydrogen + fluorine + carbon
→ no chlorine

HFO
→ hydrogen + fluorine + carbon
→ carbon-carbon double bond
→ no chlorine

HYDROCARBON
→ hydrogen + carbon

The three most important environmental reminders are:

CHLORINE IN CFC / HCFC
→ NONZERO ODP

ZERO ODP
≠
ZERO GWP

LOW GWP
≠
AUTOMATICALLY SAFE, LEGAL, OR SUITABLE

1. Master Refrigerant-Family Comparison

Do not use this table to determine the ASHRAE safety class or Section 608 pressure category of a specific refrigerant. Those are refrigerant-specific properties and are developed in 11.4 - Refrigerant Pressure and Safety Classification Reference.md.

2. Environmental Metrics

2.1 Ozone-Depletion Potential

Ozone-depletion potential (ODP) compares the ability of a substance to deplete stratospheric ozone with the impact of CFC-11.

The project reference is:

CFC-11
→ ODP = 1.0

A larger ODP means greater ozone-depletion impact per unit mass relative to the reference.

Family-Level ODP Pattern

Exam Memory Rule

CFC / HCFC
→ CHLORINE
→ ODP > 0

HFC / HFO
→ NO CHLORINE
→ ODP = 0

2.2 Global-Warming Potential

Global-warming potential (GWP) compares the climate effect of a greenhouse gas with carbon dioxide over a stated time horizon.

The project reference is:

CO₂
→ GWP = 1

GWP values must be interpreted with their:

• Time horizon.
• Scientific assessment.
• Regulatory source.
• Refrigerant composition if a blend is involved.

Therefore:

A GWP number is not complete unless its basis is known.

Two technically credible sources can report different GWP values for the same refrigerant because they may rely on different scientific assessment reports or regulatory conventions.

2.3 Zero ODP Does Not Mean Zero Climate Impact

A refrigerant can have:

ODP = 0

and still have:

HIGH GWP

HFCs are the most important course example.

The absence of chlorine prevents ozone-depletion behavior associated with CFCs and HCFCs, but it does not determine atmospheric heat-trapping effect.

Therefore:

OZONE PROTECTION
and
CLIMATE PROTECTION
→ RELATED BUT DIFFERENT QUESTIONS

2.4 Direct and Indirect Climate Effects

Direct Climate Effect

A direct climate effect occurs when refrigerant is released and the refrigerant itself contributes to greenhouse forcing.

Important factors include:

• Refrigerant GWP.
• Charge size.
• Leakage.
• Service emissions.
• End-of-life recovery.
• Refrigerant losses during equipment life.

Indirect Climate Effect

An indirect climate effect can arise from the energy required to operate the equipment.

For example, two refrigerants with different direct GWPs can also produce different system efficiencies depending on:

• Equipment design.
• Operating conditions.
• Heat-exchanger design.
• Compressor design.
• Controls.
• Application.

Therefore:

A refrigerant comparison should not be reduced to a single GWP number when evaluating overall environmental performance.

For EPA 608 examination preparation, however, the high-priority distinction remains:

ODP
→ ozone-depletion comparison

GWP
→ climate-impact comparison

3. CFC Refrigerants

3.1 Family Definition

A chlorofluorocarbon (CFC) contains:

• Carbon.
• Chlorine.
• Fluorine.

It does not contain hydrogen.

Examples used throughout the course include:

• CFC-11 / R-11
• CFC-12 / R-12

Other historical CFC refrigerants include R-113, R-114, and R-115.

3.2 Environmental Behavior

CFCs are important historically because they combine:

• Significant ozone-depletion potential.
• Long atmospheric lifetime.
• Often substantial GWP.

When a CFC reaches the stratosphere, ultraviolet radiation can break the molecule apart and release chlorine. The chlorine can participate in catalytic ozone-destruction reactions.

The course reference substance for ODP is:

CFC-11
→ ODP = 1.0

3.3 Typical Historical Use

Representative historical uses include:

CFCs remain important for EPA 608 study because technicians may encounter:

• Legacy equipment.
• Recovered refrigerant.
• Reclaimed refrigerant.
• Historical records.
• Older study-guide questions.
• Regulatory phaseout history.

3.4 Service Reminder

PHASED OUT PRODUCTION / IMPORT
≠
PERMISSION TO VENT

A legacy appliance containing CFC refrigerant must still be serviced, recovered, and disposed of under the applicable current refrigerant-management requirements.

Do not mix recovered CFC refrigerant with other refrigerants.

4. HCFC Refrigerants

4.1 Family Definition

A hydrochlorofluorocarbon (HCFC) contains:

• Hydrogen.
• Carbon.
• Chlorine.
• Fluorine.

Common course examples:

• HCFC-22 / R-22
• HCFC-123 / R-123

4.2 Why HCFC ODP Is Lower Than CFC ODP

HCFCs still contain ozone-depleting chlorine.

However, the presence of hydrogen makes many HCFCs more likely to break down in the lower atmosphere before reaching the stratosphere.

Therefore:

HCFC ODP
→ generally LOWER than comparable CFC ODP

but:

HCFC ODP
≠ 0

4.3 Typical Historical and Legacy Use

The U.S. HCFC production/import phaseout is staged. The project already distinguishes:

• R-22/HCFC-142b production/import ending in 2020.
• Remaining U.S. HCFC production/import scheduled to end in 2030.

This does not automatically prohibit continued operation of every existing HCFC appliance.

4.4 Service Reminder

Technicians working on HCFC equipment must remember:

• HCFC refrigerant remains an ozone-depleting substance.
• Refrigerant must be recovered when required.
• Existing equipment may continue to contain legacy charge.
• Recovered/recycled/reclaimed refrigerant may remain relevant where permitted.
• Do not treat an old installed system as exempt simply because new production/import is phased down or phased out.
• Do not use obsolete historical leak-rate values merely because the equipment uses R-22.

5. HFC Refrigerants

5.1 Family Definition

A hydrofluorocarbon (HFC) contains:

• Hydrogen.
• Fluorine.
• Carbon.

HFCs contain no chlorine.

Therefore:

HFC
→ ODP = 0

Common examples include:

• R-32.
• R-125.
• R-134a.
• R-143a.

Common HFC blends include:

• R-404A.
• R-407A.
• R-407C.
• R-410A.
• R-507A.

5.2 Environmental Behavior

HFCs were widely adopted because they do not deplete stratospheric ozone.

However:

HFC
→ ZERO ODP

does not mean:

HFC
→ LOW GWP

Many widely used HFCs and HFC blends have substantial 100-year GWP values.

This is why HFC climate impacts are addressed separately from the ozone-depletion phaseout framework.

5.3 Current U.S. Climate-Regulatory Context

The American Innovation and Manufacturing Act provides a separate federal framework for HFCs.

At the family level, remember:

AIM ACT
→ HFC PRODUCTION / CONSUMPTION PHASEDOWN
→ REFRIGERANT MANAGEMENT
→ TECHNOLOGY TRANSITIONS

This should not be confused with the ozone-depleting-substance phaseout of CFCs and HCFCs.

CFC / HCFC PHASEOUT
→ OZONE PROTECTION

HFC PHASEDOWN
→ CLIMATE PROTECTION

5.4 Service Reminder

HFC refrigerants can still be subject to:

• Section 608 technician-certification requirements.
• Recovery requirements.
• Sales restrictions for non-exempt substitutes.
• Safe-disposal requirements.
• Venting restrictions unless a specific substitute/end use is exempt.
• Separate current HFC management and technology-transition provisions.

Do not assume that:

ODP = 0
→ venting allowed

or:

HFC
→ every HFC is interchangeable

6. HFO Refrigerants

6.1 Family Definition

A hydrofluoroolefin (HFO) contains:

• Hydrogen.
• Fluorine.
• Carbon.
• At least one carbon-carbon double bond.

The double bond makes the molecule unsaturated and generally less atmospherically persistent than a comparable saturated HFC.

Course examples include:

• HFO-1234yf.
• HFO-1234ze(E).

6.2 Environmental Behavior

HFOs contain no chlorine.

Therefore:

HFO
→ ODP = 0

Many HFOs also have very low GWP because their atmospheric lifetimes are comparatively short.

This makes HFO chemistry important in the transition toward lower-GWP refrigeration and air-conditioning technologies.

6.3 Pure HFO Versus HFO-Containing Blend

Do not assume every refrigerant marketed as part of a lower-GWP transition is a pure HFO.

Examples:

R-1234yf
→ pure HFO refrigerant

R-454B
→ blend containing HFC + HFO components

A blend must be identified by its actual designation and composition.

6.4 Service Reminder

Many HFOs and HFO-containing blends require special attention to:

• Flammability classification.
• Equipment approval.
• Charge limits.
• Ignition-source control.
• Service-tool suitability.
• Recovery-equipment suitability.
• Cylinder and storage requirements.
• Manufacturer procedures.
• Current SNAP/end-use status.
• Current building and mechanical codes.

Do not use the word HFO as a substitute for checking the specific refrigerant’s safety class.

7. Hydrocarbon Refrigerants

7.1 Family Definition

Hydrocarbon refrigerants contain only:

• Hydrogen.
• Carbon.

Important course examples:

• R-290 — propane
• R-600a — isobutane

7.2 Environmental Behavior

Common hydrocarbon refrigerants have:

ODP = 0

and very low direct GWP compared with many traditional fluorocarbon refrigerants.

Their environmental advantage does not eliminate the major safety issue:

HYDROCARBON
→ FLAMMABLE

7.3 Typical Use

Representative current applications include:

• Household refrigeration.
• Small self-contained commercial refrigeration.
• Selected heat-pump or HVAC/R applications where specifically permitted and designed for the refrigerant.

Application depends on:

• Equipment design.
• Charge amount.
• End-use acceptability.
• Codes and standards.
• Location.
• Ventilation.
• Ignition-source controls.

7.4 Service Reminder

Do not assume a hydrocarbon refrigerant may be used as a generic replacement for a nonflammable fluorocarbon.

A technician must verify:

• The appliance was designed or properly approved for the refrigerant.
• Applicable charge limits.
• Correct recovery equipment.
• Correct electrical/service practices.
• Ignition-source control.
• Ventilation.
• Leak-detection procedure.
• Current regulatory/end-use acceptability.

A product marketed with a name suggesting it is a direct replacement for R-22 or another refrigerant is not automatically an approved substitute.

8. Carbon Dioxide — R-744

8.1 Identity

R-744
→ carbon dioxide
→ CO₂

R-744 is treated as a natural refrigerant in HVAC/R discussions.

8.2 Environmental Behavior

R-744 has:

ODP = 0

and:

GWP = 1

because carbon dioxide is the reference gas for GWP.

Do not describe carbon dioxide as a zero-GWP refrigerant.

8.3 Typical Use

Representative applications include:

• Supermarket refrigeration.
• Commercial refrigeration.
• Refrigerated transport.
• Heat pumps.
• Specialized industrial systems.

8.4 Service Reminder

The low GWP does not imply low hazard.

R-744 systems can involve:

• Very high pressure.
• Rapid pressure rise in trapped liquid or warm isolated sections.
• Dry-ice formation under certain depressurization conditions.
• Oxygen-displacement/asphyxiation concerns in occupied or confined areas.

System components and service equipment must be rated for the applicable R-744 pressures.

Detailed pressure classification belongs in Section 11.4.

9. Ammonia — R-717

9.1 Identity

R-717
→ ammonia
→ NH₃

Ammonia is a natural refrigerant widely associated with industrial refrigeration.

9.2 Environmental Behavior

R-717 has:

ODP = 0

and a very low direct climate impact in the environmental comparison framework used by this course.

Its environmental characteristics do not remove its major safety hazards.

9.3 Typical Use

Representative applications include:

• Industrial refrigeration.
• Food processing.
• Cold storage.
• Ice plants.
• Large warehouse systems.
• Process refrigeration.

9.4 Service Reminder

Ammonia requires special attention to:

• Toxicity.
• Exposure response.
• Ventilation.
• Leak detection.
• Respiratory protection.
• Emergency planning.
• Material compatibility.
• System-specific operating procedures.

Do not generalize halocarbon service procedures to ammonia systems.

10. Water — R-718

10.1 Identity

R-718
→ water
→ H₂O

Water can serve as a refrigerant in specialized systems.

10.2 Environmental Behavior

Under the EPA refrigerant-table convention used in this course:

ODP = 0

and:

GWP = 0

for R-718 as a refrigerant entry.

This refrigerant-table convention should not be confused with atmospheric-science discussions of water vapor as a greenhouse constituent.

10.3 Typical Use

Representative uses include:

• Absorption refrigeration.
• Specialized vacuum/low-pressure refrigeration processes.

Water requires very low operating pressures to evaporate at common refrigeration temperatures.

10.4 Service Reminder

R-718 systems are specialized.

Do not assume that a water-refrigerant system uses the same:

• Pressure range.
• Compressor arrangement.
• Leak behavior.
• Recovery method.
• Charging procedure.

as a conventional halocarbon vapor-compression system.

11. Pure Refrigerants and Refrigerant Blends

Chemical family and blend behavior are different classifications.

A refrigerant may be:

• One pure compound.
• A blend of compounds from the same broad chemical family.
• A blend containing components from more than one family.

11.1 Pure Refrigerants

Examples used in the course:

11.2 Zeotropic Blends

ASHRAE 400-series designations are generally associated with zeotropic blends.

Examples include:

• R-404A.
• R-407A.
• R-407C.
• R-410A as a near-azeotropic 400-series blend.
• R-448A.
• R-449A.
• R-454B.

A zeotropic blend can have:

• Different liquid and vapor compositions.
• Temperature glide.
• Bubble-point and dew-point temperatures.

Technician memory rule:

ZEOTROPIC BLEND
→ normally withdraw from supply cylinder as LIQUID

to help maintain the intended composition.

11.3 Azeotropic Blends

ASHRAE 500-series designations are generally associated with azeotropic blends.

Example:

• R-507A.

At the azeotropic composition, the mixture behaves much more like a single substance during phase change.

11.4 Near-Azeotropic Blends

A near-azeotropic blend is technically a zeotropic blend with very small temperature glide.

A common course example is:

• R-410A.

Do not conclude that:

SMALL GLIDE
→ PURE REFRIGERANT

R-410A remains a blend.

12. Representative Environmental Values Already Used in the Course

The following values are carried forward from Section 2.3 so that Module 11 remains consistent with the existing course.

Important: These are the representative values already adopted in Section 2.3 for course consistency. GWP values can differ among scientific assessments and regulatory tables. Do not combine values from different source bases without identifying the assessment and time horizon.

For the future refrigerant-by-refrigerant quick-reference table in Section 11.17, every numeric environmental value should identify its source basis explicitly.

13. Historical and Current Family Transition

The broad refrigerant transition taught in the course can be summarized as:

CFC
→ high ozone impact
→ production/import phaseout

HCFC
→ lower but nonzero ozone impact
→ transitional family
→ staged production/import phaseout

HFC
→ zero ODP
→ widespread replacement family
→ climate concern / AIM Act phasedown

HFO + LOWER-GWP BLENDS + NATURAL REFRIGERANTS
→ expanding use where technically and legally appropriate

This sequence is a family-level teaching model, not a rule that every appliance must be converted from one family to the next.

A technician must not infer retrofit suitability from the transition sequence.

14. Phaseout, Phasedown, and Existing Equipment

These words must not be confused.

Phaseout

A phaseout generally reduces and ultimately ends specified production/import or consumption of a controlled substance according to the controlling program and schedule.

For CFCs and HCFCs, the course primarily discusses ozone-protection phaseout.

Phasedown

A phasedown reduces production and consumption without necessarily requiring the controlled substance to reach zero.

For regulated HFCs, the AIM Act uses a phasedown framework.

Existing Equipment

Neither word automatically means:

ALL EXISTING EQUIPMENT MUST BE IMMEDIATELY REMOVED

Existing-equipment treatment depends on the applicable:

• Regulation.
• Refrigerant.
• End use.
• Service rule.
• Technology-transition provision.
• Availability of recovered/reclaimed material.
• Manufacturer guidance.
• State/local requirements.

15. Environmental Property Is Not Safety Classification

Do not use ODP or GWP to infer toxicity or flammability.

Examples:

LOW GWP
→ may still be flammable

Hydrocarbon refrigerants demonstrate this clearly.

ZERO ODP
→ may still have toxicity concern

Ammonia demonstrates this clearly.

LOW GWP
→ may still operate at very high pressure

R-744 demonstrates this clearly.

Therefore:

ENVIRONMENTAL CLASSIFICATION
≠
SAFETY CLASSIFICATION
≠
PRESSURE CLASSIFICATION

See:

• 11.4 - Refrigerant Pressure and Safety Classification Reference.md
• 11.17 - Common Refrigerant Quick Reference.md

for the corresponding specific-property lookups.

16. Refrigerant Family Does Not Determine Certification Type

EPA Section 608 certification is primarily based on the appliance category, not simply on refrigerant family.

Examples:

• R-134a can appear in more than one type of equipment.
• An HFC refrigerant does not automatically mean Type II.
• A low-pressure chiller can use a refrigerant from a different family than an older low-pressure chiller.
• A hydrocarbon refrigerant does not automatically define the certification type.
• Universal certification is not a refrigerant family.

The technician should determine:

APPLIANCE
→ SMALL APPLIANCE?
→ PRESSURE CATEGORY?
→ TYPE I / TYPE II / TYPE III

rather than:

REFRIGERANT FAMILY
→ ASSUME CERTIFICATION TYPE

17. Service and Retrofit Warnings by Family

18. High-Priority EPA 608 Exam Associations

19. Common Mistakes and Confusing Points

Mistake 1 - Assuming Every Fluorinated Refrigerant Depletes Ozone

Fluorine does not create the CFC/HCFC ozone-depletion mechanism by itself.

HFCs and HFOs:

contain fluorine
+
contain no chlorine
→ ODP = 0

Mistake 2 - Assuming HCFC Means Zero ODP

HCFCs contain chlorine.

Therefore:

HCFC
→ ODP > 0

even though the ODP is generally lower than for the CFCs they helped replace.

Mistake 3 - Assuming HFC Means Low GWP

Many HFCs and HFC blends have significant GWP.

HFC
→ ZERO ODP

does not imply:

HFC
→ LOW GWP

Mistake 4 - Treating HFC and HFO as the Same Family

HFOs contain a carbon-carbon double bond.

That structural difference generally gives HFOs shorter atmospheric lifetimes than conventional HFCs.

Mistake 5 - Assuming Zero ODP Means No Environmental Concern

A zero-ODP refrigerant can still have:

• Significant GWP.
• High leakage impact.
• Energy-efficiency implications.
• End-of-life recovery requirements.

Mistake 6 - Assuming a Low-GWP Refrigerant Is Automatically Safe

A low-GWP refrigerant may be:

• Flammable.
• Toxic.
• High pressure.
• Subject to charge limits.
• Unacceptable for a specific end use.

Mistake 7 - Calling CO₂ a Zero-GWP Refrigerant

Carbon dioxide is the GWP reference gas.

R-744
→ GWP = 1

Mistake 8 - Assuming Every Natural Refrigerant Is Nonflammable and Nontoxic

Examples:

R-290
→ flammable

R-717
→ toxic

R-744
→ high pressure + asphyxiation concern

Mistake 9 - Treating a Family as a Blend Classification

HFC identifies chemical family.

Zeotropic or azeotropic identifies mixture phase behavior.

For example:

R-407C
→ HFC blend
→ zeotropic

Mistake 10 - Assuming All 400-Series Blends Have the Same Glide

The 400 series indicates zeotropic blend designation, but temperature glide varies by blend.

R-410A is near-azeotropic with small glide.

R-407C has more noticeable glide.

Mistake 11 - Assuming Phaseout Means Existing Equipment Is Automatically Illegal

A production/import phaseout does not automatically prohibit continued possession or operation of every installed appliance.

Check the current rule and the specific end use.

Mistake 12 - Assuming Phasedown Means Phaseout

The AIM Act HFC framework is a phasedown of production and consumption.

It is not the same ozone-protection phaseout framework used for CFCs and HCFCs.

20. Fast Family Memory Map

CFC
C + Cl + F
→ ODP > 0
→ legacy / phased-out production-import context

HCFC
H + C + Cl + F
→ ODP > 0 but generally lower than CFC
→ transitional / legacy

HFC
H + F + C
→ ODP = 0
→ GWP can be high
→ AIM Act climate context

HFO
H + F + C + C=C
→ ODP = 0
→ generally very low GWP
→ verify flammability

HYDROCARBON
H + C
→ ODP = 0
→ very low GWP
→ FLAMMABILITY

R-744
CO₂
→ ODP = 0
→ GWP = 1
→ VERY HIGH PRESSURE

R-717
NH₃
→ ODP = 0
→ very low direct climate impact
→ TOXICITY

R-718
H₂O
→ ODP = 0
→ specialized low-pressure use

21. Cross-Reference Guide

References

Current EPA Sources

1. U.S. Environmental Protection Agency, Ozone-Depleting Substances, current project verification August 14, 2026.

2. U.S. Environmental Protection Agency, Phaseout of Class I Ozone-Depleting Substances, current project verification August 14, 2026.

3. U.S. Environmental Protection Agency, Phaseout of Class II Ozone-Depleting Substances, current project verification August 14, 2026.

4. U.S. Environmental Protection Agency, Background on HFCs and the AIM Act, current project verification August 14, 2026.

5. U.S. Environmental Protection Agency, Frequent Questions on the Phasedown of Hydrofluorocarbons, current project verification August 14, 2026.

6. U.S. Environmental Protection Agency, Questions and Answers About SNAP, current project verification August 14, 2026.

7. U.S. Environmental Protection Agency, Refrigerant Safety, current project verification August 14, 2026.

Course Cross-References

8. 2.3 - Refrigerant Families ODP and GWP

9. 2.4 - Clean Air Act and Montreal Protocol

10. 3.2 - Pure Refrigerants and Refrigerant Blends

11. 3.3 - Temperature Glide Bubble Point and Dew Point

12. 6.4 - Refrigerant Safety Classifications

13. 8.2 - Refrigerant Pressure Classifications