11.4 - Refrigerant Pressure and Safety Classification Reference

Module: Standalone Reference Appendices and Instructor Resources
Purpose: Consolidated reference for EPA Section 608 appliance pressure classifications and ASHRAE refrigerant safety classifications
Regulatory verification date: August 14, 2026
Primary regulatory authority for pressure classifications: 40 CFR §§ 82.152 and 82.161
Primary technical authority for safety classifications: ANSI/ASHRAE Standard 34-2024, together with current published addenda
Field-use warning: Pressure and safety classifications can affect certification, equipment selection, tools, installation, and service procedures. Verify the exact refrigerant and current controlling references before making a field-service or design decision.

How to Use This Reference

This appendix brings together two classification systems that students frequently confuse:

EPA SECTION 608 PRESSURE CLASSIFICATION
→ low / medium / high / very high pressure

and:

ASHRAE SAFETY CLASSIFICATION
→ A1 / A2L / A2 / A3 / B1 / B2L / B2 / B3

These systems answer different questions.

The most important rule in this file is:

PRESSURE CLASS
≠
SAFETY CLASS
≠
ENVIRONMENTAL CLASS
≠
CERTIFICATION TYPE BY ITSELF

1. EPA Section 608 Pressure Classification

1.1 The Regulatory Reference Condition

Current Section 608 definitions classify appliances principally by the liquid-phase saturation pressure of the refrigerant at 104°F.

The reference temperature is:

$$104{}^{\circ }\text{F}=40{}^{\circ }\text{C}$$

The regulatory pressure values are stated in:

psia
→ pounds per square inch ABSOLUTE

not:

psig
→ pounds per square inch GAUGE

A service gauge reading during operation is therefore not, by itself, the value used to classify the appliance.

1.2 Master Pressure-Classification Table

*The certification direction assumes the appliance is otherwise within the applicable Section 608 Type II or Type III scope. Small appliances, MVACs, MVAC-like appliances, and other regulatory boundaries must be checked separately.

Fast Memory Line

<45
→ LOW

45–170
→ MEDIUM

170–355
→ HIGH

>355
OR critical temperature <104°F
→ VERY HIGH

Always attach the complete reference:

psia
at 104°F

2. Why 104°F Saturation Pressure Is Used

A refrigerant’s saturation pressure changes with temperature.

For a given refrigerant:

temperature changes
→ saturation pressure changes

Therefore, a pressure category cannot be defined consistently by saying only:

"this refrigerant runs at high pressure"

The regulation uses a fixed comparison condition:

104°F

so that different refrigerants can be classified on a common basis.

The classification is based on a refrigerant property, not on one operating snapshot.

This means that the following do not define the Section 608 pressure category:

• Suction pressure observed during operation.
• Discharge/head pressure observed during operation.
• Outdoor temperature during the service call.
• Evaporator temperature during the service call.
• Condenser pressure during the service call.
• Nameplate design pressure.
• Factory pressure-test rating.
• Refrigerant charge size.
• Compressor horsepower.
• Equipment tonnage.
• Refrigerant chemical family.

3. psia Versus psig

Section 608 pressure-category definitions use absolute pressure.

Near standard atmospheric conditions:

$$P_{\text{abs}}\approx P_{\text{gauge}}+14.7\text{psi}$$

For example, a saturation pressure shown on a chart as:

$$200\text{psig}$$

corresponds approximately to:

$$214.7\text{psia}$$

near standard atmospheric pressure.

That numerical difference can matter when comparing a value with a regulatory threshold.

Exam Rule

REGULATORY PRESSURE CLASSIFICATION
→ CHECK psia

SERVICE GAUGE
→ usually reads psig

Do not compare a psig chart value directly with a psia regulatory threshold without first checking the pressure reference.

See 11.2 - Acronyms Symbols Units and Conversions.md for a fuller treatment of gauge and absolute pressure.

4. Low-Pressure Appliances

A low-pressure appliance uses a refrigerant with a liquid-phase saturation pressure:

below 45 psia at 104°F

Current regulatory examples include:

• R-11.
• R-123.
• R-113.
• R-245fa.

Low-pressure appliances are associated with Type III certification when the appliance/activity falls within the Section 608 technician-certification requirement.

Typical course examples include:

• Low-pressure chillers.
• Centrifugal chillers using low-pressure refrigerants.
• Systems that can operate below atmospheric pressure on the low side.

Important Distinction

The term:

LOW-PRESSURE APPLIANCE

does not mean only:

"the suction gauge happens to be below 0 psig"

The regulatory category comes from the refrigerant’s defined saturation-pressure property.

5. Medium-Pressure Appliances

A medium-pressure appliance uses a refrigerant with a liquid-phase saturation pressure:

between 45 psia and 170 psia at 104°F

Current regulatory examples include:

• R-114.
• R-124.
• R-12.
• R-134a.
• R-500.

For Section 608 technician certification, medium-pressure appliances are included within Type II when the appliance/activity is otherwise within Type II scope.

Important Current-Rule Point

Some public-facing summaries use the shorthand:

Type II
→ high-pressure appliances

However, the current regulatory certification language at 40 CFR § 82.161 expressly includes:

medium-pressure
+
high-pressure
+
very-high-pressure

appliances within Type II, except for the listed exclusions such as small appliances, MVACs, and MVAC-like appliances.

6. High-Pressure Appliances

A high-pressure appliance uses a refrigerant with a liquid-phase saturation pressure:

between 170 psia and 355 psia at 104°F

Current regulatory examples include:

• R-22.
• R-407A.
• R-407C.
• R-410A.
• R-502.

These appliances are generally associated with Type II certification when the appliance is not excluded from the Type II scope.

High-Priority Example

R-410A
→ HIGH PRESSURE

Do not classify R-410A as very high pressure merely because its normal field operating pressures are high compared with R-22.

7. Very-High-Pressure Appliances

A very-high-pressure appliance meets either of two refrigerant-property conditions:

critical temperature below 104°F

or:

liquid-phase saturation pressure above 355 psia at 104°F

Current regulatory examples include:

• R-13.
• R-23.
• R-503.
• R-508A.
• R-508B.

These appliances are generally associated with Type II certification when the appliance/activity is within Type II scope.

Why the Critical-Temperature Criterion Matters

The critical temperature is the temperature above which a substance cannot be liquefied by pressure alone.

If the refrigerant’s critical temperature is below the regulatory reference temperature of 104°F, it independently satisfies the very-high-pressure definition.

Therefore:

VERY HIGH PRESSURE
→ not determined only by comparing one pressure number with 355 psia

The critical-temperature pathway must also be considered.

8. Pressure Category and Certification Type

The pressure category is important, but it is not the first and only classification question.

A practical examination sequence is:

1. IDENTIFY THE APPLIANCE

2. CHECK WHETHER IT IS A SMALL APPLIANCE

3. CHECK MVAC / MVAC-LIKE / OTHER BOUNDARIES

4. IF PRESSURE CLASSIFICATION CONTROLS:
   LOW → TYPE III
   MEDIUM / HIGH / VERY HIGH → TYPE II

Small-Appliance Exception

A qualifying small appliance is Type I for maintenance, service, and repair even though the refrigerant itself may have a pressure relationship that would otherwise fall into a medium-, high-, or very-high-pressure range.

Therefore:

PRESSURE CATEGORY
→ important

but:

PRESSURE CATEGORY ALONE
→ not enough to classify every appliance

The complete appliance-classification process is developed in 11.5 - Appliance Type and Certification Decision Guide.md.

9. Pressure Classification Is Not High Side / Low Side

These phrases sound similar but describe different concepts.

High Side / Low Side

These describe locations within a refrigeration system.

HIGH SIDE
→ generally condenser side of the metering device

LOW SIDE
→ generally evaporator/suction side

High-Pressure / Low-Pressure Appliance

These are Section 608 appliance classifications based on the refrigerant property definitions.

A high-pressure appliance still has:

• A high side.
• A low side.

A low-pressure appliance also has regions of different operating pressure.

Therefore:

HIGH SIDE
≠
HIGH-PRESSURE APPLIANCE

10. ASHRAE Refrigerant Safety Classification

ASHRAE Standard 34 assigns refrigerant safety groups using two classifications:

TOXICITY
+
FLAMMABILITY

The result is an alphanumeric safety group such as:

A1
A2L
A2
A3
B1
B2L
B2
B3

The decoding rule is:

LETTER
→ TOXICITY

NUMBER / NUMBER-LETTER
→ FLAMMABILITY

11. Master Safety-Classification Matrix

This matrix should be read in two directions.

Across the table:

1 → 2L → 2 → 3

the flammability classification increases.

Down the table:

A → B

the toxicity classification changes from lower to higher toxicity.

12. Toxicity Classes A and B

12.1 Class A

A
→ lower toxicity

Within the Standard 34 framework, Class A corresponds to the lower-toxicity side of the classification system. The commonly used dividing criterion is an occupational exposure limit of 400 ppm or greater.

Class A does not mean:

• Nontoxic.
• Safe to breathe.
• Safe at any concentration.
• No asphyxiation hazard.
• No cardiac effect.
• No frostbite hazard.
• No decomposition-product hazard.

A Class A refrigerant can still displace oxygen or create other serious exposure hazards.

12.2 Class B

B
→ higher toxicity

Within the Standard 34 framework, Class B corresponds to the higher-toxicity side, associated with an occupational exposure limit below 400 ppm.

A B-class refrigerant may require greater attention to:

• Allowable refrigerant concentration.
• Equipment location.
• Ventilation.
• Detection.
• Machinery-room provisions.
• Emergency procedures.
• PPE.
• Respiratory protection planning.
• Applicable codes and standards.

Memory Rule

A
→ LOWER TOXICITY

B
→ HIGHER TOXICITY

Do not memorize:

A = safe
B = unsafe

That interpretation is too simplistic and technically incorrect.

13. Flammability Class 1

1
→ no flame propagation under the specified classification test conditions

Class 1 does not mean:

• The refrigerant can never be involved in a fire-related hazard.
• The refrigerant cannot thermally decompose.
• Hot work is automatically safe.
• Every service tool is automatically suitable.
• Exposure hazards disappear.

A refrigerant can be:

A1

and still require normal refrigerant safety precautions.

14. Flammability Class 2L

2L
→ lower flammability
+
low burning velocity

Class 2L is a subclass within the lower-flammability framework.

The Standard 34 framework includes a maximum burning-velocity criterion of:

10 cm/s or lower

under the specified test conditions.

The L is important.

A2L
≠
A1

A2L refrigerants have a flammability classification and require appropriate ignition-control and service practices.

Representative Course Examples

• R-32 - A2L.
• R-454B - A2L.
• R-1234yf - A2L.
• R-717 ammonia - B2L.

15. Flammability Class 2

2
→ lower flammability

Class 2 refrigerants exhibit flame propagation under the applicable classification test and satisfy the Class 2 flammability criteria.

At the course-reference level, remember:

2
→ lower flammability

and:

2L
→ lower flammability
+
low-burning-velocity subclass

A representative course example is:

R-512A
→ A2

When exact classification affects actual service or design, verify the current Standard 34 classification and addenda.

16. Flammability Class 3

3
→ higher flammability

Class 3 represents the higher-flammability end of the Standard 34 classification framework.

Common examples include hydrocarbons such as:

R-290 propane
→ A3

R-600a isobutane
→ A3

These refrigerants may have favorable environmental properties, but their flammability requires equipment and procedures specifically designed for that hazard.

17. Interpreting the Common Safety Groups

A1

A1
=
lower toxicity
+
Class 1

Representative course example:

R-410A

Remember:

• Lower toxicity does not mean harmless.
• Class 1 does not remove pressure or exposure hazards.
• A1 does not describe ODP or GWP.

A2L

A2L
=
lower toxicity
+
lower flammability
+
low burning velocity

Representative course examples:

• R-32.
• R-454B.
• R-1234yf.

High-priority service implication:

A2L
→ treat as a flammable-refrigerant classification

and verify equipment/tool suitability, ventilation, ignition control, and current code requirements.

A2

A2
=
lower toxicity
+
Class 2 lower flammability

Representative course example:

• R-512A.

Do not confuse A2 with A2L.

The L subclass has an additional low-burning-velocity criterion.

A3

A3
=
lower toxicity
+
higher flammability

Representative course examples:

• R-290 propane.
• R-600a isobutane.

The A does not reduce the importance of the Class 3 flammability hazard.

B1

B1
=
higher toxicity
+
Class 1

Representative course example:

• R-514A.

The Class 1 flammability classification does not eliminate the higher-toxicity concern.

B2L

B2L
=
higher toxicity
+
lower flammability
+
low burning velocity

Representative course example:

• R-717 ammonia.

This classification combines two important hazard dimensions:

higher toxicity
+
flammability

B2

B2
=
higher toxicity
+
Class 2 lower flammability

A B2 refrigerant combines higher toxicity with a Class 2 flammability classification.

B3

B3
=
higher toxicity
+
higher flammability

B3 represents the combination of the higher-toxicity class and higher-flammability class.

This classification is useful for understanding the full matrix even when it is not a major refrigerant example in the EPA 608 question bank.

18. Representative Safety-Class Table Used in This Course

Field-use warning: This table is a course reference, not a substitute for the current edition of ASHRAE Standard 34 and its current addenda. Refrigerant classifications can be added or revised as the standard is maintained.

19. Historical 2L Classification Warning

Older HVAC/R references may show some refrigerants under a general Class 2 designation that are now recognized in the 2L subclass.

Important course examples include:

R-32
→ current A2L

R-717
→ current B2L

R-1234yf
→ current A2L

This is a good example of why a technician should not rely on an old chart when an exact safety classification controls a current service decision.

Use:

CURRENT STANDARD 34
+
CURRENT PUBLISHED ADDENDA

rather than an undated refrigerant chart.

20. Pressure Class and Safety Class Are Independent

Consider R-410A.

Section 608 pressure classification:

R-410A appliance
→ HIGH-PRESSURE example

ASHRAE safety classification:

R-410A
→ A1

These statements describe different properties.

The first concerns:

saturation pressure

The second concerns:

toxicity + flammability

Therefore:

HIGH PRESSURE
does not mean
HIGH FLAMMABILITY

and:

LOW PRESSURE
does not mean
LOW TOXICITY

Never infer one classification from the other.

21. Safety Class Is Not ODP or GWP

The safety group does not encode environmental impact.

For example:

A1

does not tell you:

• ODP.
• GWP.
• CFC/HCFC/HFC/HFO family.
• Whether the refrigerant is subject to a phaseout or phasedown.
• Whether it is acceptable for a particular end use.
• Whether Section 608 permits venting.

Likewise:

A2L

does not mean:

low GWP by definition

Many current lower-GWP transition refrigerants happen to be A2L, but GWP is not encoded in the safety-group notation.

See 11.3 - Refrigerant Family and Environmental Comparison.md for the environmental classification framework.

22. Safety Class Is Not EPA Certification Type

The following is incorrect:

A2L
→ Type II

Safety class does not determine certification type.

EPA certification depends on the appliance/activity.

Similarly:

A3
→ Type I

is not a universal rule.

A hydrocarbon refrigerant may be used in a qualifying small appliance, but the safety group itself does not create Type I classification.

Use the appliance-classification process in Section 11.5.

23. Safety Class Is Not Permission to Use a Refrigerant

A Standard 34 designation and safety group do not by themselves establish that a refrigerant may be used in every application.

Actual use can depend on:

• EPA SNAP status and use conditions.
• Equipment listing.
• Manufacturer approval.
• Building code.
• Mechanical code.
• Fire code.
• Electrical requirements.
• Charge limits.
• Occupancy.
• Installation location.
• Ventilation.
• Refrigerant-detection requirements.
• State and local adoption of applicable standards.

Therefore:

ASHRAE CLASSIFICATION
→ identifies refrigerant safety characteristics

but:

ASHRAE CLASSIFICATION
≠ universal legal approval for every use

24. Standard 34 and Standard 15 Serve Different Roles

A useful distinction is:

ASHRAE STANDARD 34
→ What is the refrigerant designation and safety classification?

ASHRAE STANDARD 15
→ How must refrigeration systems using refrigerants be safely designed, installed, and operated?

Standard 34 establishes:

• Refrigerant designations.
• Safety classifications.
• Refrigerant concentration limits.
• Related classification information.

Standard 15 applies refrigerant properties within a system-safety framework.

A technician may also need to follow:

• Product-safety standards.
• Equipment listing instructions.
• Manufacturer service literature.
• State/local code requirements.
• EPA requirements.

25. Classification and Service Tools

Safety classification can affect the suitability of service equipment.

Do not assume that tools used for an A1 refrigerant are automatically suitable for:

• A2L refrigerants.
• A2 refrigerants.
• A3 refrigerants.
• B-class refrigerants.

Depending on the refrigerant and equipment, verify the suitability of:

• Recovery machine.
• Vacuum pump.
• Leak detector.
• Refrigerant scale.
• Manifold/gauges.
• Hoses.
• Electrical service tools.
• Ventilation equipment.
• Spark/ignition control procedures.

The manufacturer’s rated refrigerant compatibility and the applicable safety/code requirements control.

26. Refrigerant Classification Verification Workflow

For actual field use, use a deliberate verification sequence.

STEP 1
Identify the refrigerant from the equipment nameplate
or other reliable equipment documentation.

STEP 2
For Section 608 pressure category:
check current 40 CFR §82.152.

STEP 3
For safety group:
check current ANSI/ASHRAE Standard 34
plus published addenda.

STEP 4
Read the current SDS and manufacturer service information.

STEP 5
Check equipment listing and tool compatibility.

STEP 6
Check applicable ASHRAE 15, product-safety,
building, mechanical, fire, electrical,
state, and local requirements.

STEP 7
Check current EPA SNAP/end-use requirements
when substitute acceptability or use conditions matter.

Do Not Use as the Sole Authority

Do not make a field decision from only:

• An old textbook.
• An undated pocket chart.
• A social-media post.
• A refrigerant seller’s advertisement.
• A cylinder color.
• A trade name.
• A memory from an older certification course.

27. Pressure-Classification Quick Lookup

Low Pressure

<45 psia at 104°F
→ LOW
→ Type III direction

Examples:

R-11
R-123
R-113
R-245fa

Medium Pressure

45–170 psia at 104°F
→ MEDIUM
→ Type II direction

Examples:

R-114
R-124
R-12
R-134a
R-500

High Pressure

170–355 psia at 104°F
→ HIGH
→ Type II direction

Examples:

R-22
R-407A
R-407C
R-410A
R-502

Very High Pressure

>355 psia at 104°F
OR
critical temperature <104°F
→ VERY HIGH
→ Type II direction

Examples:

R-13
R-23
R-503
R-508A
R-508B

28. Safety-Classification Quick Lookup

Toxicity

A
→ lower toxicity

B
→ higher toxicity

Flammability

1
→ no flame propagation under specified test conditions

2L
→ lower flammability + low burning velocity

2
→ lower flammability

3
→ higher flammability

Common Combined Groups

A1
→ lower toxicity + Class 1

A2L
→ lower toxicity + Class 2L

A2
→ lower toxicity + Class 2

A3
→ lower toxicity + Class 3

B1
→ higher toxicity + Class 1

B2L
→ higher toxicity + Class 2L

B2
→ higher toxicity + Class 2

B3
→ higher toxicity + Class 3

29. High-Priority Comparison Table

30. EPA 608 Exam Focus

Pressure Numbers to Memorize

104°F
→ classification reference temperature

45 psia
→ low / medium boundary

170 psia
→ medium / high boundary

355 psia
→ high / very-high pressure criterion

Representative Pressure Examples

R-123
→ LOW

R-134a
→ MEDIUM

R-22
→ HIGH

R-410A
→ HIGH

R-23
→ VERY HIGH

Safety Symbols to Memorize

LETTER
→ TOXICITY

NUMBER / 2L
→ FLAMMABILITY

A
→ LOWER TOXICITY

B
→ HIGHER TOXICITY

1
→ NO FLAME PROPAGATION UNDER TEST CONDITIONS

2L
→ LOWER FLAMMABILITY + LOW BURNING VELOCITY

2
→ LOWER FLAMMABILITY

3
→ HIGHER FLAMMABILITY

Representative Safety Examples

R-410A
→ A1

R-32 / R-454B
→ A2L

R-512A
→ A2

R-290 / R-600a
→ A3

R-514A
→ B1

R-717
→ B2L

31. Common Mistakes and Confusing Points

Mistake 1 - Calling R-410A Very High Pressure

R-410A has high operating pressures, but the current Section 608 definition lists it as a representative high-pressure refrigerant.

Mistake 2 - Forgetting Medium Pressure

Current regulations explicitly define medium-pressure appliances.

R-134a is a representative medium-pressure refrigerant.

Medium-pressure appliances fall under Type II certification when the other Type II conditions are satisfied.

Mistake 3 - Comparing psig With a psia Threshold

The pressure-category thresholds are in psia.

Service gauges normally read psig.

Mistake 4 - Using Suction Pressure to Classify the Appliance

Suction pressure changes with load and operating conditions.

It is not the regulatory classification criterion.

Mistake 5 - Using Head Pressure to Classify the Appliance

Head pressure also changes with operating conditions.

It is not the fixed 104°F saturation-property classification criterion.

Mistake 6 - Confusing High Side With High-Pressure Appliance

A high-pressure appliance has both a high side and a low side.

The terms describe different ideas.

Mistake 7 - Assuming Family Determines Pressure Category

The labels:

CFC
HCFC
HFC
HFO
HC

do not by themselves tell you the Section 608 pressure category.

Mistake 8 - Assuming Pressure Category Determines Safety Class

A high-pressure refrigerant is not automatically more flammable or more toxic than a low-pressure refrigerant.

Mistake 9 - Reading A as Nonflammable

The letter describes toxicity, not flammability.

Mistake 10 - Reading 1 as Nontoxic

The number describes flammability, not toxicity.

Mistake 11 - Calling A2L Nonflammable

A2L has a flammability classification.

The 2L identifies lower flammability with a low-burning-velocity criterion.

Mistake 12 - Calling A3 Highly Toxic

The A means lower toxicity.

The 3 means higher flammability.

Mistake 13 - Assuming A1 Means Harmless

A1 refrigerants can still create:

• Oxygen-displacement hazards.
• Frostbite.
• High-pressure release hazards.
• Cardiac effects.
• Thermal-decomposition hazards.

Mistake 14 - Using an Old Safety Chart

Older references may not show the current 2L classifications.

Always verify current Standard 34 and published addenda.

Mistake 15 - Treating Safety Class as the Complete Code Requirement

Safety class is an input.

Actual requirements can also depend on:

• Charge.
• Occupancy.
• Installation.
• Equipment listing.
• Ventilation.
• Detection.
• Ignition control.
• Adopted code edition.
• Local requirements.

Mistake 16 - Applying Type II Before Checking Small-Appliance Status

A qualifying small appliance remains Type I for maintenance, service, and repair even if its refrigerant property falls within a pressure range associated with Type II.

32. Field-Use Verification Warning

This appendix is designed for:

• EPA Section 608 study.
• Classroom instruction.
• Fast technical review.
• Recognition of the major classification systems.

It is not a substitute for current standards, regulations, SDS information, equipment listings, or manufacturer service instructions.

Before using a refrigerant classification for actual service, design, retrofit, charging, recovery, or installation:

Verify the refrigerant designation and classification using current authoritative sources.

This is especially important for:

• New lower-GWP refrigerants.
• A2L refrigerants.
• A3 refrigerants.
• B-class refrigerants.
• Newly assigned refrigerant blends.
• Applications affected by updated product-safety standards or codes.
• Equipment manufactured under newer refrigerant-transition requirements.

ANSI/ASHRAE Standard 34 is maintained on continuous maintenance, and published addenda can introduce or revise refrigerant data between full editions.

33. Cross-Reference Guide

References

Current Federal Regulatory Sources

1. U.S. Environmental Protection Agency, 40 CFR § 82.152 - Definitions, current as verified August 14, 2026.
   https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-82/subpart-F/section-82.152

2. U.S. Environmental Protection Agency, 40 CFR § 82.161 - Technician Certification, current as verified August 14, 2026.
   https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-82/subpart-F/section-82.161

3. U.S. Environmental Protection Agency, Section 608 Technician Certification Requirements, current project verification August 14, 2026.
   https://www.epa.gov/section608/section-608-technician-certification-requirements

4. U.S. Environmental Protection Agency, Refrigerant Safety, updated March 5, 2026.
   https://www.epa.gov/snap/refrigerant-safety

Current ASHRAE Sources

5. ASHRAE, ANSI/ASHRAE Standard 34-2024 - Designation and Safety Classification of Refrigerants, current edition identified by ASHRAE and verified August 14, 2026.

6. ASHRAE, Standards Addenda, showing published addenda to Standard 34-2024, including addenda through June 30, 2026, as verified August 14, 2026.
   https://www.ashrae.org/technical-resources/standards-and-guidelines/standards-addenda

7. ASHRAE, Refrigeration Resources - Standards 15 and 34, current description of the complementary roles of Standards 15 and 34.
   https://www.ashrae.org/technical-resources/bookstore/ashrae-refrigeration-resources

8. ASHRAE, Refrigerant Designations, refrigerant-designation and safety-classification information with a warning to use the latest Standard 34 and addenda.
   https://www.ashrae.org/technical-resources/standards-and-guidelines/ashrae-refrigerant-designations

Course Cross-References

9. 6.4 - Refrigerant Safety Classifications

10. 8.2 - Refrigerant Pressure Classifications

11. 11.2 - Acronyms Symbols Units and Conversions

12. 11.3 - Refrigerant Family and Environmental Comparison