Study guide
3.2 Refrigerant Classification, ASHRAE Numbering, and Safety Groups
EPA 608 Technician Certification Exam
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1 Introduction to EPA 608 Certification
1.1 What EPA 608 Is and Who Needs It 1.2 Exam Format, Scoring, and Administration 1.3 How to Study for EPA 608
2 Regulations and the Clean Air Act
2.1 Clean Air Act Overview 2.2 Penalties and Enforcement 2.3 Montreal Protocol and International Agreements 2.4 AIM Act and HFC Phasedown Schedule 2.5 SNAP Program and Refrigerant Transitions
3 Refrigerants and Ozone Science
3.1 The Science of Ozone Depletion (ODP and GWP) 3.2 Refrigerant Classification, ASHRAE Numbering, and Safety Groups 3.3 Common Refrigerants: Properties, Applications, and Phaseout Status 3.4 Refrigerant Blends: Glide, Fractionation, and Liquid Charging
4 The Refrigeration Cycle
4.1 The Basic Refrigeration Cycle 4.2 System Components in Detail 4.3 Heat Transfer and Pressure-Temperature Relationships
5 Refrigerant Safety and Handling
5.1 Refrigerant Hazards and Health Effects 5.2 Safe Handling Practices, PPE, and Cylinders 5.3 A2L (Mildly Flammable) Refrigerant Safety
6 Recovery, Recycling, and Reclaiming
6.1 The Three Rs: Recover, Recycle, Reclaim 6.2 Recovery Equipment Requirements 6.3 Required Levels of Evacuation 6.4 Refrigerant Sales Restrictions and Recordkeeping
7 Leak Detection and Repair
7.1 Leak Detection Methods 7.2 Leak Repair Requirements and Trigger Rates 7.3 Leak-Rate Calculation, Recordkeeping, and Reporting
8 Type I — Small Appliances
8.1 What Counts as a Small Appliance 8.2 Type I Recovery Requirements 8.3 Type I Procedures, Access Valves, and the Open-Book Exam
9 Type II — High-Pressure Appliances
9.1 What Type II Covers: High-Pressure System Overview 9.2 Type II Recovery Methods and Required Evacuation Levels 9.3 Leak Detection, the Repair Triggers, and Recordkeeping 9.4 The R-22 Phaseout, Retrofits, and the Move to Lower-GWP A2Ls
10 Type III — Low-Pressure Appliances
10.1 Low-Pressure System Fundamentals 10.2 Purge Units and Air Management 10.3 Type III Recovery and Procedures 10.4 Type III Leak Testing
11 10. Disposal, Shipping, and Compliance
11.1 Equipment Disposal Requirements 11.2 Refrigerant Shipping and Transport 11.3 Compliance Checklist and Best Practices
12 Final Review and Exam Strategy
12.1 High-Yield Core Section Review 12.2 Type I vs Type II vs Type III: Side-by-Side Review 12.3 How the Exam Works and Exam-Day Strategy
3.2 Refrigerant Classification, ASHRAE Numbering, and Safety Groups
Key Takeaways Explain This Topic AI
CFC, HCFC, HFC, HFO, and natural refrigerants are distinguished by chemistry — the presence or absence of chlorine is what drives ODP and the phaseout schedule
CFCs are Class I ozone-depleting substances (production ended 1996); HCFCs are Class II (phasing out by 2030); HFCs are not ODS but are phased down by the AIM Act for GWP
ASHRAE Standard 34 assigns a two-character safety group: a letter for toxicity (A = lower, B = higher) and a number for flammability (1 = none, 2L = mild, 2 = flammable, 3 = high)
R-410A and R-134a are A1 (safest handling class); R-32, R-454B, and R-1234yf are A2L (mildly flammable); propane R-290 is A3; ammonia R-717 is B2L
R-number series indicate composition: 400 = zeotropic blends, 500 = azeotropic blends, 700 = inorganic naturals, 1200 = HFOs
Last updated: June 2026
Every refrigerant on the EPA 608 exam belongs to a chemical family and carries an ASHRAE safety classification. These two systems answer different questions: the chemical family tells you how the refrigerant affects the atmosphere and when it is being phased out, while the ASHRAE safety group tells you how dangerous it is to handle. Knowing both — and how to read an R-number — lets you reason about any refrigerant you encounter, even unfamiliar ones.
The Five Chemical Families
The single most important variable across these families is chlorine . Chlorine is what destroys ozone, so the industry has moved progressively from chlorine-heavy CFCs toward chlorine-free naturals and HFOs.
CFCs — Chlorofluorocarbons (Class I ODS)
Contain chlorine, fluorine, and carbon — no hydrogen.
Highest ODP and extremely stable, persisting 50-100+ years in the atmosphere.
Production banned in developed countries since 1996 .
Examples: R-11, R-12, R-113, R-114, R-502.
HCFCs — Hydrochlorofluorocarbons (Class II ODS)
Contain hydrogen, chlorine, fluorine, and carbon .
Lower ODP than CFCs — the hydrogen makes them less stable so they degrade faster.
R-22 production ended January 1, 2020 ; full HCFC phaseout by 2030 .
Examples: R-22, R-123, R-124, R-141b.
HFCs — Hydrofluorocarbons
Contain hydrogen, fluorine, and carbon — no chlorine .
Zero ODP but often high GWP .
Subject to the AIM Act HFC phasedown.
Examples: R-134a, R-404A, R-407C, R-410A, R-32.
HFOs — Hydrofluoroolefins
Like HFCs but with a carbon-to-carbon double bond, which makes them break down quickly in the lower atmosphere.
Zero ODP and very low GWP (often below 10).
The newest synthetic generation.
Examples: R-1234yf, R-1234ze.
Natural Refrigerants
Naturally occurring substances: R-717 (ammonia), R-744 (CO2), R-290 (propane), R-600a (isobutane) .
Zero ODP and generally very low GWP.
ODS Classification: Class I vs. Class II
EPA divides ozone-depleting substances (ODS) into two regulatory classes.
- Class Substances ODP Status
- Class I CFCs, halons, carbon tetrachloride, methyl chloroform Highest Phased out (1996)
- Class II HCFCs Lower Phasing out (2030)
A frequent exam point: HFCs are not ozone-depleting substances and appear in neither class — they are regulated separately under the AIM Act for their climate impact.
ASHRAE Standard 34 Safety Classification
ASHRAE Standard 34 assigns every refrigerant a two-character safety group. The letter rates toxicity and the number rates flammability .
Letter — toxicity (based on the occupational exposure limit, OEL):
- A = lower toxicity (OEL ≥ 400 ppm)
- B = higher toxicity (OEL < 400 ppm)
Number — flammability:
- 1 = no flame propagation
- 2L = lower flammability (burning velocity ≤ 10 cm/s)
- 2 = flammable
- 3 = higher flammability
The 2L subclass matters enormously for 2026 service work because the industry is shifting from A1 refrigerants to mildly flammable A2L refrigerants like R-454B and R-32 in new equipment.
- Safety Group Toxicity Flammability Examples
- A1 Lower None R-22, R-134a, R-410A, R-404A
- A2L Lower Mild R-32, R-454B, R-1234yf
- A2 Lower Flammable R-152a
- A3 Lower High R-290 (propane), R-600a (isobutane)
- B1 Higher None R-123
- B2L Higher Mild R-717 (ammonia)
- Reading the R-Number
The R-number encodes the molecule for single-component refrigerants (methane and ethane series):
- Hundreds digit = (number of carbon atoms) − 1
- Tens digit = (number of hydrogen atoms) + 1
- Units digit = number of fluorine atoms
For blends and naturals, the series tells you the type:
- Series Type Examples
- 400 Zeotropic blend (has glide) R-401A, R-404A, R-407C, R-410A
- 500 Azeotropic blend (no glide) R-500, R-502, R-507A
- 600 Organic compounds R-600a (isobutane)
- 700 Inorganic naturals (number = molecular weight) R-717 (ammonia, MW 17), R-744 (CO2, MW 44)
- 1200 HFOs (unsaturated) R-1234yf, R-1234ze
Worked Example: Decode R-134a . Hundreds digit = 1, so carbons = 1 + 1 = 2 . Tens digit = 3, so hydrogens = 3 − 1 = 2 . Units digit = 4, so fluorines = 4 . The molecule is therefore C2H2F4 (tetrafluoroethane), and the trailing "a" denotes the specific isomer. Because it contains no chlorine, its ODP is 0 — exactly what the family classification (HFC) already told you. This cross-check, reading both the number and the family, is the kind of reasoning the Core section rewards.
When a new refrigerant appears, classify it in two passes: first the chemistry (does it contain chlorine? → ODP and phaseout), then the ASHRAE group (how toxic, how flammable? → handling precautions). That two-pass habit will carry you through any classification question on the exam.