EPA 608 Core Exam: Study Guide for 2026

What the Core exam is

Every Section 608 certification starts with Core. It's 25 multiple-choice questions on the rules and safety practices that apply to every kind of equipment: why refrigerants are regulated, what you may and may not release, how refrigerant is recovered, recycled and reclaimed, and how to handle cylinders without getting hurt.

You need 70% to pass: 18 out of 25. Core plus Type I, Type II or Type III gets you certified for that type. Pass all four sections and you hold a Universal card. The certification doesn't expire.

Core is a closed-book test, proctored by an EPA-approved certifying organization. Some organizations offer a Type I-only test by mail; a Core section passed that way does not count toward Universal certification.

Ozone depletion: why refrigerants are regulated

The ozone layer sits in the stratosphere, roughly 6 to 30 miles up, and filters out most of the sun's UV-B radiation. The problem is chlorine. When a CFC or HCFC drifts up there, UV light breaks the molecule apart and frees its chlorine atoms, and a single chlorine atom can destroy up to 100,000 ozone molecules.

That's why the exam sorts refrigerants by what's in them:

• CFCs (R-11, R-12): chlorine, fluorine and carbon. The highest ozone depletion potential (ODP). R-11 is the yardstick, with an ODP of 1.0.
• HCFCs (R-22, R-123): the hydrogen makes them break down sooner, so their ODP is lower, but not zero.
• HFCs (R-134a, R-410A) and HFOs (R-1234yf): no chlorine, so an ODP of zero. HFCs are regulated anyway, for their high global warming potential (GWP), measured against carbon dioxide at 1.

Quick check: can you tell an HCFC from an HFC at a glance? Take the free 10-question Core test and find out.

The Clean Air Act, the Montreal Protocol and the AIM Act

The Montreal Protocol is the international treaty that phased out ozone-depleting substances, first CFCs, then HCFCs. Its Kigali Amendment extends the deal to a phasedown of HFCs.

In the U.S., Section 608 of the Clean Air Act is the law behind the rules you're tested on (40 CFR Part 82, Subpart F). The big ones for Core:

• No venting. You may not knowingly release CFCs, HCFCs or their substitutes, HFCs included, while servicing, repairing or disposing of equipment. Only de minimis releases are allowed: the small amount that escapes during a good faith effort to recover, like the puff when you connect or disconnect hoses with low-loss fittings. A few substitutes, such as ammonia, are exempt.
• Certification. Maintaining, servicing, repairing or disposing of equipment in ways that could release these refrigerants takes a Section 608 card.
• Sales restriction. Since January 1, 2018, refrigerant, HFCs included, may only be sold to certified technicians, with a few narrow exceptions.

What changed in 2026

The AIM Act (2020) lets EPA phase down HFC production and consumption by 85% over 15 years. Under it, EPA's Emissions Reduction and Reclamation rule brought leak repair back to HFC equipment: since January 1, 2026, appliances with 15 lbs or more of an HFC refrigerant (or a substitute with a GWP above 53) must be repaired when their annual leak rate passes 30% for industrial process refrigeration, 20% for commercial refrigeration, and 10% for comfort cooling and other appliances. Residential and light commercial AC and heat pumps are exempt (more in the AIM Act leak repair guide).

Recover, recycle, reclaim

Expect at least one question on these three words, and expect the wrong answers to be the other two definitions. Learn them the way the regulation writes them:

• Recover: remove refrigerant, in any condition, and store it in an external container, without necessarily testing or processing it.
• Recycle: clean refrigerant for reuse by oil separation and single or multiple passes through devices such as replaceable-core filter-driers, which cut moisture, acidity and particulates. This usually happens on the job site.
• Reclaim: reprocess refrigerant to all of the AHRI Standard 700 specifications and verify it by chemical analysis. That's the job of an EPA-certified reclaimer.

Recovered refrigerant may go back into equipment of the same owner, but it may not be sold to someone else unless it has been reclaimed.

On the job: getting refrigerant out faster

• Recover liquid first: it moves most of the charge in the least time.
• Chill the recovery cylinder and warm the appliance to widen the pressure difference.
• Pull Schrader valve cores and use short, large-diameter hoses.

Recovery cylinders and shipping

• Refillable recovery cylinders are DOT-approved and painted gray with a yellow top. Disposable cylinders are never used for recovery.
• Never fill a recovery cylinder above 80% of its capacity by weight: liquid expands as it warms and needs room.
• Evacuate a recovery cylinder before you put refrigerant in it.
• Cylinders carry a pressure relief valve. Never heat one with an open flame, and haul them upright and secured.
• An empty disposable cylinder gets recovered to 0 psig, made unusable, and recycled as scrap metal.

Evacuation, leak testing and moisture

Evacuation pulls air (non-condensables) and moisture out of a system. Moisture matters more than it looks: mixed with CFCs or HCFCs it forms hydrochloric and hydrofluoric acids that eat a compressor from the inside.

• Read a deep vacuum with a micron gauge, not a compound gauge. 500 microns is the usual target for dehydration.
• Isolate the pump and watch the gauge. A reading that climbs and keeps climbing is a leak; one that climbs and levels off means moisture is still boiling out.
• Pressurize for a leak test with dry nitrogen through a regulator. Never oxygen or compressed air: under pressure, mixed with compressor oil, they can explode.

Safety

• Wear safety glasses and gloves: liquid refrigerant causes frostbite on contact.
• Refrigerant vapor is heavier than air and pushes oxygen out of a closed room. In a basement mechanical room a big leak can suffocate you before you smell anything.
• CFCs and HCFCs exposed to an open flame or high heat break down into toxic gases, phosgene and acids among them.
• ASHRAE Standard 34 classes refrigerants by toxicity (A lower, B higher) and flammability (1 none, 2L mild, 2, 3 high). R-410A is A1. R-32 and R-454B, now replacing high-GWP HFCs in new equipment, are A2L: mildly flammable, so ignition sources and ventilation matter.

How to study for Core

1. Learn recover, recycle and reclaim word for word.
2. Know which refrigerant families contain chlorine, and why that matters.
3. Memorize the handful of numbers: 80% cylinder fill, 25 questions, 18 to pass.
4. Practice in 25-question blocks, the way the real section is built.

The EPA 608 Exam Prep app has 100+ Core questions with the reasoning after every answer, works with no signal, and its Readiness Ring estimates your chance of clearing 70% in Core and every other section. Core is free.