EPA 608 refrigerant types explained (2026): what the exam actually tests

If you came here to figure out which certification to take, that is a different question. Start at certification types or the what is EPA 608 overview. This page owns the chemistry that the Core exam tests.

One page unifies the refrigerant families, the ASHRAE safety classes, zeotropic and azeotropic blends, oil compatibility, R-410A, and the 2026 A2L transition, all framed as the questions the Core and Type II sections throw at you. The naming convention is your cheat code. R-12 is CFC-12, R-22 is HCFC-22, R-134a is HFC-134a, R-1234yf is HFO-1234yf. Decode the number, name the family, answer the question.

What are the main refrigerant families on the EPA 608 exam?

The exam does not want you to memorize 60 refrigerants. It wants you to sort any refrigerant into one of five families by the atoms it carries. Walk the chain CFC to HCFC to HFC to HFO to hydrocarbon, and the ozone story tells itself.

CFCs (chlorofluorocarbons) contain chlorine, fluorine, and carbon. The exam names are R-11, R-12, R-500, and R-502, all fully phased out under the Montreal Protocol. Because they carry no hydrogen, they are chemically stable, so they survive the lower atmosphere and drift into the stratosphere intact. Once UV light frees it, a single chlorine atom can destroy up to 100,000 ozone molecules.

HCFCs (hydrochlorofluorocarbons) add hydrogen to the mix. That hydrogen makes them less stable, so more of the molecule breaks down before it reaches the ozone layer, giving them a lower ODP. R-22 (the old residential AC workhorse), R-123 (centrifugal chillers), and R-124 are the ones to know.

HFCs (hydrofluorocarbons) drop chlorine entirely: just hydrogen, fluorine, and carbon. No chlorine means an ODP of zero. R-32, R-134a, R-404A, R-407C, and R-410A all live here, and they all require POE oil. HFOs (hydrofluoroolefins) add a carbon-to-carbon double bond, and R-1234yf is the headliner with a GWP under 1 and an A2L safety rating. Hydrocarbons and naturals round out the set: R-290 (propane) and R-600a (isobutane) are A3, and R-717 (ammonia) is B2L.

How does the ASHRAE safety classification system work (and what is A2L)?

Every refrigerant on the exam carries a two-part safety code from ASHRAE Standard 34, and the Core and Type II sections ask you to read it. The letter is toxicity. The number is flammability. Get both and you can classify anything on the sheet.

Toxicity is simple: A means lower toxicity (occupational exposure limit of 400 ppm or higher), B means higher toxicity (OEL below 400 ppm). Flammability runs on a scale. A rating of 1 is no flame propagation, 2L is mildly flammable with a burning velocity at or below 10 cm/s, 2 is flammable, and 3 is highly flammable. The lowercase "L" in 2L stands for low burning velocity, and that single letter is the whole 2026 story.

A1 is the safest class and where most legacy refrigerants sit: R-410A, R-22, R-134a, R-404A, and R-407C. A2L is the new arrival that trips up techs raised on A1-only systems. R-32, R-454B, and R-1234yf are A2L: low toxicity, mildly flammable, but with a slow, low-energy burn that is a fundamentally different hazard from a propane tank. A2L is a mild, controllable class, not "just flammable," which is exactly why the exam added it.

The extremes still matter. A3 covers the hydrocarbons like R-290 propane and R-600a isobutane, which ignite readily. B1 is R-123, toxic but non-flammable. B2L is ammonia (R-717), toxic and mildly flammable at once.

Zeotropic vs azeotropic blends: glide, fractionation, and liquid charging

Blends separate techs who memorized from techs who understood. The tested distinction is whether the components in a blend behave as one substance or as several, because that decides how you charge it and how it leaks.

Zeotropic blends carry ASHRAE 400-series numbers and mix refrigerants with different boiling points. As the blend evaporates or condenses, its temperature slides across a range instead of holding steady. That range is temperature glide, the difference between the dew point and the bubble point at constant pressure. R-407C runs about 11.5°F of glide (dew point 21.94°F, bubble point 10.44°F), which you have to account for when you measure superheat and subcooling. R-404A, despite being a 400-series blend, is near-azeotropic with roughly 1°F of glide.

Azeotropic blends carry 500-series numbers and behave as a single substance with essentially zero glide. R-502 is the exam favorite: R-22 at 48.8% and R-115 at 51.2% by weight. R-500 is another. Both boil and condense as if they were one refrigerant.

Glide creates two problems the exam loves. First, fractionation: because the components have different vapor pressures, they leak at different rates, and the composition left in the system drifts away from spec. That hits R-407C hardest. Second, charging: you must charge a zeotropic blend as a liquid, never vapor, or the most volatile component enters first and the ratio is wrong from the start. Never combine refrigerants yourself. A self-mixed blend is illegal under EPA rules, cannot be reclaimed, and carries fines.

Which oil goes with which refrigerant?

Pick the wrong oil and the system starves. Refrigerant oil has to be miscible with its refrigerant, meaning it blends and travels with it. If it does not, the oil never returns from the evaporator, pools in the low side, and starves the compressor. Miscibility is a requirement, not a preference.

Mineral oil pairs with the old chlorine-bearing refrigerants, CFCs and HCFCs like R-12 and R-22. Alkylbenzene (AB) oil also serves CFC and HCFC systems, mixes with mineral oil, and bridges some retrofits. Neither belongs in a modern HFC system.

POE (polyolester) is the oil the exam ties to R-410A and every other HFC and HFO: R-32, R-454B, R-134a. Two rules define it. POE cannot be mixed with any other oil, and POE is hygroscopic, meaning it pulls moisture straight out of the air. That absorbed water reacts with the refrigerant through hydrolysis to form acid, so POE systems have to stay sealed and dehydrated. Leave a POE container open on the truck and you have already started degrading it.

Two more round out the list. PAG (polyalkylene glycol) is automotive R-134a only, not stationary HVAC, so do not carry a car-AC habit onto a rooftop unit. PVE (polyvinyl ether) is an alternative to POE for HFC and HFO systems where POE does not fit.

R-410A: the refrigerant the Type II exam leans on

If Type II has a signature refrigerant, it is R-410A, and the exam tests it from several angles at once. It is a near-azeotropic HFC blend of R-32 and R-125 at roughly 50/50, with an ODP of 0, a GWP of 2,088, and an ASHRAE A1 rating. It runs on POE oil.

The number that matters in the field and on the test is pressure. R-410A operates about 60% higher than R-22. At 95°F ambient, that looks like roughly 135 PSIG suction against R-22's 70 PSIG, and around 380 PSIG discharge against R-22's 260 PSIG. Those pressures are exactly why you cannot retrofit R-22 equipment to R-410A. The components are not built to hold it.

Watch the trap. R-410A carries a 400-series number, which screams zeotropic and significant glide. In practice it behaves near-azeotropically, with glide so small it charges and reads like a single-component refrigerant. Expect a question that dangles "large temperature glide" as a tempting wrong answer for R-410A.

R-410A also sets up the 2026 storyline. It is the high-GWP HFC being phased down under the AIM Act, and knowing its chemistry is the on-ramp to its A2L replacements. Recover it under 40 CFR Part 82 and the Clean Air Act, the same as any regulated refrigerant, and route it to a certified reclaimer rather than the atmosphere. The Core study guide covers the recovery rules that pair with this chemistry.

What color are refrigerant cylinders now?

Older study material actively lies to you on cylinder color, so read this section as a correction. Since January 2020, under AHRI Guideline N (published 2017), all new virgin refrigerant containers ship in one uniform color: RAL 7044 silk gray, a light green-gray. The unique color-per-refrigerant system is gone.

The change was a voluntary U.S. guideline, not a federal mandate, driven by refrigerant proliferation. As the number of refrigerants grew, the old color codes stopped helping and started causing confusion, and more than half of surveyed handlers said so. Flammable refrigerants (A2L, A2, A3) get one added marker: a red band on the cylinder.

The exception is the one the exam cares about most. Recovery cylinders were not touched by the 2020 shift. They stay gray body with a yellow top, the DOT standard for recovery and recycling, and that combination is the single most-tested cylinder fact on the Core exam.

Legacy colors still appear in old prep books, so recognize them as history, not current practice: R-22 light green, R-410A rose or pink, R-134a sky blue, R-404A orange. If a study source lists those as current, it is out of date.

How does the 2026 AIM Act change what you'll be tested on?

The 2026 exam added content that older prep material does not cover, and most of it flows from one law. The AIM Act (American Innovation and Manufacturing Act of 2020) phases down HFC production, enforced under the same 40 CFR Part 82 and Clean Air Act framework you already know from Core.

The dates matter. New R-410A residential split systems could not be manufactured or imported after January 1, 2025. A July 2026 EPA final rule then clarified the follow-through: pre-2025 R-410A equipment can still be installed until that inventory depletes, existing systems are grandfathered with no forced replacement, and service refrigerant stays legal for systems already in the field. This is a manufacturing restriction, not an outright ban.

The replacements are A2L, which is why that safety class jumped onto the exam. R-454B (68.9% R-32 plus 31.1% R-1234yf, GWP 466) is the primary swap for most residential manufacturers, and R-32 (GWP 675) dominates mini-splits. No R-410A system can be retrofitted to A2L. A2L means new equipment engineered for it.

So the 2026 Core and Type II sections now test ASHRAE 34 A2L classification, the January 1, 2025 manufacturing cutoff, A2L leak detection, and the brazing and ventilation precautions that come with a mildly flammable refrigerant. Study the full timeline in the AIM Act changes guide and the equipment shift in the low-GWP refrigerants guide.

EPA 608 refrigerant types FAQ