EPA 608 — Complete Study Guide (2026)

Introduction

Every technician who buys or handles refrigerant must first pass the Core section, and Core is the largest single block on the certification. It is also the section that makes the rest of the exam make sense, because it explains why the rules exist. Before you can reason about a recovery percentage or a leak‑repair deadline, you need to know what refrigerant does to the ozone layer, what the Clean Air Act demands of you, and what the words recover, recycle, and reclaim actually mean.

Core is heavily definitional. The questions reward a candidate who knows the vocabulary cold — who does not confuse an HCFC with an HFC, who can state the difference between recovering and recycling in one sentence, and who remembers which refrigerants can no longer be manufactured. This chapter walks through ozone chemistry, the venting prohibition, the three R's, the production phase‑outs, and refrigerant blends, with the heaviest focus on the ideas the Core section tests most often.

Learning objectives

After working through this chapter you should be able to:

• Explain how chlorine from CFCs and HCFCs destroys stratospheric ozone, and rank refrigerant families by ozone depletion potential (ODP).
• Distinguish ODP from global warming potential (GWP), and know that modern rules target both.
• State the venting prohibition — what it bans, when it took effect for CFCs/HCFCs versus their HFC substitutes, and the narrow exceptions.
• Define the three R's — recover, recycle, reclaim — precisely enough to tell them apart on a swap‑the‑definitions question.
• Recall the production phase‑out dates for CFCs and HCFCs and the direction of the AIM Act HFC phase‑down.
• Tell a zeotropic blend from an azeotropic blend, explain temperature glide, and know why zeotropic blends are charged as a liquid.
• Explain what the SNAP program does and why you may never mix refrigerants.

Part A — Ozone depletion and refrigerants

The stratospheric ozone layer, roughly 6 to 30 miles above the earth, absorbs most of the sun's harmful ultraviolet (UV) radiation. That shielding is why the ozone layer matters to life on the surface — and why releasing refrigerant is treated as a serious problem rather than a harmless puff of gas.

The chemistry is worth understanding because the exam tests it. Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are chemically stable. That stability is exactly what makes them dangerous to ozone: instead of breaking down near the ground, they survive long enough to drift up into the stratosphere, where intense UV light breaks them apart and frees chlorine atoms. A single chlorine atom acts as a catalyst and can destroy tens of thousands of ozone molecules before it is finally removed from the cycle. That catalytic multiplication is the reason even a small leak matters, and the reason the whole regulatory structure is built around not letting refrigerant escape.

A refrigerant's ozone depletion potential (ODP) measures this damage on a relative scale, with CFC‑11 set at 1.0 as the reference point. The pattern to memorize:

• CFCs (for example R‑11 and R‑12) contain the most chlorine and have the highest ODP.
• HCFCs (for example R‑22) contain less chlorine and do less ozone damage.
• HFCs (for example R‑410A and R‑134a) contain no chlorine at all, so their ODP is zero.

But zero ODP is not the end of the story. Refrigerants also carry a global warming potential (GWP), which rates how strongly the gas traps heat in the atmosphere relative to carbon dioxide. Many HFCs have zero ODP but very high GWP, which is why the newest wave of regulation targets them too. When you see a question ask what "modern rules limit," the answer is both ozone damage (ODP) and climate impact (GWP) — not one or the other.

Part B — Section 608 and the venting prohibition

Section 608 of the Clean Air Act, carried out through 40 CFR Part 82, is the federal law that governs the service, maintenance, repair, and disposal of stationary air‑conditioning and refrigeration equipment. (Note the word stationary: motor‑vehicle air conditioning is handled separately under Section 609.)

The centerpiece of Section 608 is the venting prohibition. Since July 1, 1992, it has been illegal to knowingly release CFC and HCFC refrigerants into the atmosphere during the service, maintenance, repair, or disposal of covered appliances. The ban was then extended to their HFC and other substitute refrigerants on November 15, 1995. In plain terms: whatever the refrigerant, you may not knowingly vent it.

The exceptions are deliberately narrow, and the exam likes to probe them:

• Good‑faith connecting and disconnecting. Small releases that happen while you are making a good‑faith effort to connect or disconnect recovery equipment are not violations.
• De minimis quantities. Tiny amounts that genuinely cannot be recovered with required equipment are not violations.
• Nitrogen is not a refrigerant. Dry nitrogen used for pressure testing, leak testing, or purging may be released to the atmosphere without violating the rule — because it is not a regulated refrigerant. Watch the wording on this one: the exception covers the nitrogen, not refrigerant in general. A question that quietly swaps "nitrogen" for "refrigerant" is testing whether you noticed.

Finally, Section 608 sets the gatekeeping rule that runs through the whole certification: anyone who maintains, services, repairs, or disposes of covered appliances must be an EPA‑certified technician. That is why you are reading this book.

Part C — The three R's: recover, recycle, reclaim

The Clean Air Act builds refrigerant conservation around three actions whose definitions are among the most heavily tested Core facts. Learn them as a ladder of increasing processing:

• Recover — to remove refrigerant from an appliance in any condition and store it in an external container. That is all recovery means. No cleaning, no testing, no processing — just get it out of the system and into a container.
• Recycle — to clean recovered refrigerant for reuse by reducing its oil, moisture, and acidity, typically with an oil separator and one or more passes through filter‑driers. Recycling happens on‑site or at a local shop and does not verify purity by chemical analysis. Recycled refrigerant is "cleaned up enough to reuse," not "proven pure."
• Reclaim — to reprocess refrigerant to the purity of new product, verified by chemical analysis against the AHRI Standard 700 specification. Only an EPA‑certified reclaimer may reclaim refrigerant.

The single most important consequence: refrigerant that changes ownership generally must be reclaimed before it is resold, while refrigerant that stays with the same owner may simply be recycled and returned to that owner's equipment. If a question asks what must happen to refrigerant before it is sold to a new owner, the answer is reclaim to AHRI 700.

Memory hook: Recover = Remove. Recycle = Reduce (oil/moisture/acid, on‑site). Reclaim = Restore to new‑product purity (lab‑verified, certified reclaimer only).

Part D — Phase‑outs and the Montreal Protocol

The 1987 Montreal Protocol is the international treaty that set the timetable for ending ozone‑depleting substances, and the United States carries out its commitments through the Clean Air Act. You do not need treaty trivia, but you do need the U.S. phase‑out dates, because they determine which refrigerants you can still buy new:

• CFC production and import in the U.S. ended January 1, 1996. That is why CFC‑12 and CFC‑11 are now available only from recovered and reclaimed stock — there is no new production.
• Virgin HCFC‑22 for new equipment ended January 1, 2010. After that date, no new HCFC‑22 equipment could be manufactured.
• Virtually all HCFC production and import ended January 1, 2020, leaving only reclaimed and previously produced supply to service older units.
• The American Innovation and Manufacturing (AIM) Act now directs EPA to phase down high‑GWP HFCs such as R‑404A and R‑410A. This phase‑down is ongoing and its specific allocation numbers change over time — teach yourself the direction (HFCs are being reduced because of high GWP), and confirm any specific quota against current EPA rules.

The practical takeaway the exam is after: as each refrigerant becomes scarce and expensive, recovery and reclamation become more important, because keeping existing equipment running increasingly depends on the recovered and reclaimed supply.

Part E — Refrigerant blends and substitutes

Many modern refrigerants are blends of two or more pure compounds, and how a blend behaves determines how you must handle it.

A zeotropic blend — such as R‑407C or R‑404A — is made of components that boil and condense at slightly different temperatures, which produces a temperature glide as the mixture changes state. Because the lighter components escape first, a leaking or vapor‑charged zeotropic blend can fractionate: its composition shifts as the more volatile parts leave. To keep the proportions correct, zeotropic blends must be charged as a liquid, not as a vapor. This is a classic exam fact — charge zeotropic blends as a liquid.

An azeotropic blend — the textbook example is R‑502 — behaves almost like a single refrigerant, with almost no glide. It does not fractionate the way a zeotropic blend does.

Two more Core facts round out the topic:

• SNAP. EPA's Significant New Alternatives Policy (SNAP) program (40 CFR Part 82, Subpart G) reviews and approves substitute refrigerants for each end use. A substitute may only be used in the applications for which it is listed acceptable — you cannot drop an approved substitute into a use it was not cleared for.
• Never mix refrigerants. Mixing different refrigerants in a system produces a charge that cannot be recycled or reclaimed and generally must be destroyed at cost. Keep every refrigerant separate, always.

Part F — Reading a refrigerant's name

You do not need to be a chemist to pass the Core section, but you will answer more questions correctly if you can look at an "R‑number" and tell which family it belongs to, because the family tells you the ozone and warming story at a glance.

• CFC — chlorofluorocarbon. Contains chlorine, fluorine, and carbon (no hydrogen). Chemically very stable, long atmospheric life, high ODP. Examples: R‑11, R‑12, R‑500, R‑502. No longer produced in the U.S.
• HCFC — hydrochlorofluorocarbon. Adds hydrogen, which makes the molecule break down lower in the atmosphere, so less chlorine reaches the stratosphere and the ODP is lower than a CFC. Example: R‑22, R‑123. Phased out (virtually all production ended 2020).
• HFC — hydrofluorocarbon. Contains no chlorine, so ODP is zero — but many have high GWP. Examples: R‑134a, R‑410A, R‑404A, R‑407C. Now being phased down under the AIM Act.
• HFO — hydrofluoro‑olefin. A newer, low‑GWP family with a carbon double bond that makes it break down quickly. Example: R‑1234yf (mobile A/C), R‑1233zd (low‑pressure chillers).

A quick literacy trick: the more hydrogen a molecule has (the "H" in HCFC/HFC), the shorter its atmospheric life and the less ozone damage it does. Chlorine is the ozone villain; hydrogen is what tames it. That single idea explains the whole CFC → HCFC → HFC progression the exam keeps testing.

Blends get a 400‑series number when they are zeotropic (R‑404A, R‑407C, R‑410A — glide, charge as liquid) and a 500‑series number when they are azeotropic (R‑500, R‑502 — behave like a single refrigerant). Knowing that "400‑series usually means glide, charge it as a liquid" is worth an easy point.

Part G — ODP, GWP, and why both matter now

Two scores describe a refrigerant's environmental cost, and modern rules use both:

• Ozone depletion potential (ODP) — damage to the ozone layer relative to CFC‑11 = 1.0. Driven by chlorine. CFCs are near 1; HCFC‑22 is a small fraction; HFCs and HFOs are 0.
• Global warming potential (GWP) — heat‑trapping strength relative to carbon dioxide = 1, measured over a 100‑year horizon. A refrigerant can have zero ODP but a GWP in the thousands. R‑410A, for example, is ozone‑safe yet has a very high GWP, which is exactly why the AIM Act targets it.

The takeaway the exam wants: the first generation of rules (the Montreal Protocol, the CFC/HCFC phase‑outs) attacked ODP; the newest rules (the AIM Act HFC phase‑down) attack GWP. If an answer choice says the modern goal is "only ozone protection," it is out of date — today's rules limit both ozone loss and climate impact.

Worked example — classify the refrigerant. A technician pulls up to a job and finds R‑134a in a system. Which family is it, what is its ODP, and is it a current phase‑down target? Reasoning: "HFC" — no chlorine — so ODP = 0; but HFCs have high GWP, so yes, R‑134a is the kind of refrigerant the AIM Act is phasing down. Answer: HFC, zero ODP, high GWP, AIM‑Act phase‑down target.