EPA 608 Core Study Guide: What the Core Section Tests and How to Prepare

What the EPA 608 Core section covers

The Core is 25 questions drawn from EPA's Group I bank, and it sits under every certification: each Type I, II or III test is 25 Core questions plus 25 for the type (Appendix D to 40 CFR Part 82, Subpart F). Appendix D names three Core areas: the environmental impact of CFCs, HCFCs and substitute refrigerants, laws and regulations, and the changing industry outlook. EPA's Test Topics page, last updated December 5, 2025, breaks that into the detailed list this guide follows.

The stakes are higher than the size suggests. ESCO Institute's 2026 exam page, checked October 28, 2026, requires 70% (18 of 25) on each section and says "You must pass the CORE section to receive any certification type." Strong type scores cannot rescue a weak Core there, which the EPA 608 passing score guide works through with an example.

EPA's Core topic list, grouped into study blocks

The numbers in these blocks (phaseout dates, the penalty, the 80% fill line, Table 1 levels) are collected with their conditions in the EPA 608 numbers guide, so this guide focuses on the ideas. When full prep opens, the 194 Core questions planned for full EPA 608 prep each come with an explanation that names the rule or EPA test topic behind the answer.

Ozone, refrigerant classes and ODP for the EPA 608 Core

EPA's glossary on the Test Topics page gives the chain of reasoning the Core tests. CFCs are very stable low in the atmosphere, rise to the stratosphere, and are broken apart by strong ultraviolet light, releasing chlorine atoms that destroy ozone. HCFCs also contain chlorine but deplete much less. HFCs contain no chlorine or bromine and have an ozone depletion potential (ODP) of zero, although some have a high global warming potential.

What to be able to do, in EPA's words: identify the class "not by chemical formulas, but idea that R-12 is a CFC, R-22 is an HCFC, R-134 is an HFC," and rank them, with CFCs above HCFCs, and HCFCs above HFCs, on ODP. EPA's glossary defines ODP against CFC-11, which is set at 1.0. HCFCs range from 0.01 to 0.1.

Newer names fit the same frame. Subpart F's definition of a "substitute" lists HFCs, perfluorocarbons, hydrofluoroolefins (HFOs), hydrofluoroethers, hydrocarbons, ammonia, carbon dioxide and their blends (40 CFR 82.152). None of these categories is a CFC or an HCFC.

Laws on the EPA 608 Core: venting, exemptions and the sales restriction

• The venting ban. No one maintaining, servicing, repairing or disposing of an appliance may knowingly vent refrigerant (40 CFR 82.154(a)(1)). Releasing refrigerant after you have recovered it is also a violation (82.154(a)(3))
• What is not a violation. EPA's venting page lists three kinds of release: "de minimis" amounts released during good-faith recovery, such as when connecting or disconnecting hoses, refrigerant emitted during normal operation (leaks, mechanical purging), and releases of substitutes EPA has exempted
• Exempt substitutes. The list in 82.154(a)(1) includes carbon dioxide, nitrogen and water in any application, ammonia in commercial or industrial process refrigeration or absorption units, and certain hydrocarbons only in named end uses, such as isobutane (R-600a) in household refrigerators
• Equipment covered. EPA's Test Topics still describe covered equipment as air conditioning and refrigeration "containing CFCs or HCFCs," which is the older scope. Since January 1, 2018, certification, evacuation and the sales restriction also cover non-exempt substitutes such as HFCs (40 CFR 82.154, 82.156, 82.161), and EPA's regulatory updates page confirms the 2020 rollback of HFC leak repair left those duties in place
• The sales restriction. Refrigerant may be sold only to certified technicians, to employers who show they employ one, and in a few listed cases such as small cans of MVAC refrigerant with a self-sealing valve (40 CFR 82.154(c))

Recover, recycle, reclaim: the three EPA 608 definitions

These three words appear in Core questions almost every time a scenario moves refrigerant around. The definitions in 40 CFR 82.152, reproduced on EPA's recover, recycle and reclaim page, decide the answer:

The practical test is ownership. Used refrigerant that changes hands must be reclaimed by an EPA-certified reclaimer first, apart from a few listed exceptions such as refrigerant still inside an appliance that is sold (40 CFR 82.154(d)). Definitions like these are what short recall cards suit best, and the 105 Core flashcards planned for EPA 608 at launch are sorted by test.

Recovery, evacuation and dehydration on the EPA 608 Core

• Two kinds of recovery equipment. Self-contained equipment removes refrigerant without help from the appliance's components; system-dependent (passive) equipment needs the appliance's own components, such as its compressor (40 CFR 82.152)
• Certified equipment. Recovery and recycling equipment must be certified, and EPA has approved AHRI and UL to certify it. Certified units carry a label saying so (EPA's equipment certification page). Equipment made or imported since January 1, 2017 for flammable refrigerants is certified under Appendix B4 (40 CFR 82.158)
• Do not mix refrigerants. EPA lists "need to avoid mixing refrigerants" as a Core recovery topic, so keep one refrigerant per recovery cylinder
• What slows recovery. EPA names ambient temperature, the size of the recovery equipment, and hose length and diameter
• Evacuate at the end of service. EPA's dehydration topic is the need to evacuate a system "to eliminate air and moisture at the end of service"

Refrigeration basics the EPA 608 Core expects

EPA wants you to know the state of the refrigerant (vapor or liquid) and its pressure at each point of the cycle, and how and when cooling happens. Fluke Corporation's application note on superheat and subcooling describes the loop: the compressor sends hot, high-pressure gas to the condenser, where it gives up heat and condenses to liquid; extra passes in the condenser cool that liquid below its boiling point (subcooling); a metering device drops the pressure so the liquid boils in the evaporator, absorbing heat from the space being cooled; and once all of it has boiled, the vapor picks up extra heat (superheat) before returning to the compressor.

So cooling happens in the evaporator, as liquid boils at low pressure. The high side runs from the compressor discharge through the condenser to the metering device, and the low side from the metering device through the evaporator back to the compressor. Fluke's note adds that many newer blends change temperature while they boil, called glide, which connects to EPA's fractionation topic: the components of a blend can leak at different rates. EPA also lists refrigeration gauges, their color codes, ranges and proper use, so learn the convention on the manifold you will use.

Substitute refrigerants and oils on the EPA 608 Core

EPA's three points here are short but easy to miss:

1. There are no true "drop-in" replacements. Retrofitting is defined in 40 CFR 82.152 as converting an appliance to another refrigerant, which may include changing lubricants, gaskets, filters, driers, valves, O-rings or components.
2. Oils have to match. EPA's examples are esters with R-134 and alkylbenzenes for HCFCs, and it warns that substitutes are incompatible with many lubricants used with CFCs and HCFCs, and the reverse.
3. Blends can fractionate. Their components may leak at different rates, so the blend left behind is no longer the original mix.

Safety and shipping on the EPA 608 Core

• Exposure risks. EPA lists oxygen deprivation, cardiac effects, frostbite and long-term hazards. Hudson Technologies' safety data sheet for R-22 (revised November 21, 2018) gives the mechanisms: vapors displace air and can asphyxiate in confined spaces, high exposure can cause central nervous system depression and cardiac arrhythmia, and contact with the liquid can cause frostbite
• Protective equipment. Gloves and goggles, and self-contained breathing apparatus "in extreme cases" (Test Topics)
• Cylinders. Recovery (reusable) cylinders must be DOT approved and are color-coded yellow and gray; disposable cylinders are never refilled. EPA lists the risk of filling a cylinder more than 80% full. Hudson's SDS classifies R-22 as a gas under pressure that "may explode if heated"
• Leak testing with nitrogen. Use nitrogen, not oxygen or compressed air, with a pressure regulator and relief valve. Arkema's tech tip explains one reason: safety data sheets for non-flammable refrigerants such as R-22 warn against pressurizing a system that still holds some refrigerant with shop air, because that can create a flammable condition, and Hudson's SDS says R-22 should not be mixed with air or oxygen above atmospheric pressure
• Shipping labels. Refrigerant cylinders need a refrigerant identification and a DOT classification tag. Hudson's SDS, for example, lists R-22 as USDOT Hazard Class 2.2, Non-Flammable Gas

Arkema's page is also a quick primer on the safety classes printed on many charts: in ASHRAE Standard 34 codes such as A1, A2L or B1, the letter refers to toxicity and the number to flammability, with 1 meaning no flame propagation and 2L, 2 and 3 marking refrigerants that are flammable to varying degrees.

Two Passy practice questions for the EPA 608 Core

These are original Passy questions, not EPA items.

1. Which statement matches the definitions in 40 CFR 82.152?

• A. Recovered refrigerant must be tested before it goes into a recovery cylinder
• B. Recycled refrigerant may be sold to any owner once it passes through filter-driers
• C. Reclaimed refrigerant has been reprocessed to AHRI 700 specifications and verified
• D. Reclaimed refrigerant may only go back into equipment owned by the same person

Answer: C. Reclaiming means reprocessing to the Appendix A specifications based on AHRI Standard 700-2016 and verifying them by analysis. Recovery happens "without necessarily testing" (A), recycling is for reuse in equipment of the same owner (B), and the same-owner limit belongs to recovered and recycled refrigerant, not reclaimed (D).

2. A repaired line set needs a leak test under pressure before it is charged. What does EPA's Core safety topic call for?

• A. Dry nitrogen through a pressure regulator, with a relief valve in place
• B. Oxygen from a torch cylinder, because it leaves no residue behind
• C. Shop compressed air, because it is dry enough for a quick test
• D. The system's own refrigerant at full cylinder pressure, for accuracy

Answer: A. EPA's topics list nitrogen rather than oxygen or compressed air, used with a pressure regulator and relief valve. Oxygen or pressurized air mixed with refrigerant traces can create a combustible condition, and EPA's Type II topics rank pure refrigerant last among leak-test gases, behind nitrogen alone and nitrogen with a trace of R-22.

How to study for the EPA 608 Core

A practical order is environment, then law, then the three R's and recovery, then safety, because later questions lean on the earlier definitions. Give Core its own study block before any type: at ESCO it gates every certification, and its questions reward exact wording, such as "same owner" in the recycling definition or "knowingly" in the venting ban.

Then test yourself. The free EPA 608 practice questions include five Core items with explanations, and the EPA 608 study plan lets you give Core extra days. Misses are most useful when you can see the rule behind them, and at launch the Weak Spot drills planned for EPA 608 are meant to target whichever test your accuracy is lowest in. Once Core is steady, move on to the EPA 608 Type I study guide or the Type II study guide, depending on your work.