EPA 608 Universal Certification Study Guide

EPA 608 Universal
Certification Study Guide

Complete 2025-2026 Prep · R-32 & R-454B Coverage · Bayou Click Media

100-Question Universal Exam 72% Pass Per Section R-32 & R-454B Fully Covered AIM Act 2025 Updated

4

Exam Sections

5

Practice Tests

60+

Flashcards

120+

Exam Questions

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Exam Overview

What the EPA 608 Universal exam covers

Universal Exam Structure

Section	Questions	To Pass
Core	25	18 correct (72%)
Type I — Small Appliances	25	21 correct (84%)
Type II — High Pressure	25	18 correct (72%)
Type III — Low Pressure	25	18 correct (72%)
TOTAL — Universal	100	Pass ALL 4

Critical Facts

Certification NEVER expires
Max penalty: $44,539/day/violation
BOTH tech AND employer can be penalized
R-22 production ended Jan 1, 2020
R-410A banned new equipment Jan 1, 2025
R-454B and R-32 are the A2L replacements
Recovery cylinders: gray body, yellow collar

The 4-Component Refrigeration Cycle

Compressor: Low-P vapor in → hot high-P vapor out
Condenser: Rejects heat to outside → high-P liquid
Metering Device: Drops pressure → cold low-P mix
Evaporator: Absorbs heat from space → vapor

Heat ALWAYS flows hot to cold. Refrigeration moves heat from inside to outside.

Vapor Compression Refrigeration Cycle

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A2L Refrigerants: R-32 & R-454B

New standard in ALL new equipment · Critical for 2025-2026 exam · 2-5 exam questions

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This is NOW Heavily Tested - Do Not Skip As of January 1, 2025, R-410A is banned in new residential equipment. Every new split system ships with R-454B or R-32. The EPA 608 exam includes 2-5 questions on A2L refrigerants. This section covers everything.

What Does A2L Mean?

            ASHRAE Standard 34 Safety Classification
            "A" = Lower toxicity — safe for humans at normal concentrations

            "2" = Flammable (but only under specific concentration conditions)

            "L" = Low burning velocity (<10 cm/s) — flames spread slowly, NOT explosive

A2L refrigerants require MUCH higher concentration to ignite than common fuels:

Substance	LFL (Lower Flammability Limit)
Butane (lighter fluid)	1.7% by volume
Propane (R-290, A3)	2.1% by volume
R-454B (A2L)	~9.5% by volume
R-32 (A2L)	14.4% by volume

R-32 needs 14.4% concentration to ignite. Butane ignites at 1.7%. A2L is much safer than A3 propane but still requires eliminating ignition sources.

Why A2L? The Big Picture

R-410A GWP = 2,088 — powerful greenhouse gas; AIM Act mandates 85% HFC reduction by 2036
A2L refrigerants have GWP of 466-675 — 68-78% lower than R-410A
The industry accepted mild flammability to achieve low GWP — no A1 alternative matches R-410A performance at comparable low GWP
R-466A is the only A1 (non-flammable) R-410A replacement — GWP 733, limited adoption
280+ million R-32 units already in service globally
New equipment is specifically listed and safety-certified for A2L — built-in protections

⚠️

You CANNOT substitute R-454B into an R-410A system. Equipment certifications, oil specs, and component ratings are NOT interchangeable.

All A2L Refrigerants — Know These for the Exam

Refrigerant	Type	GWP	LFL	Primary Use	Replaces
R-32	Pure HFC	675	14.4%	Mini-splits, ductless	R-410A
R-454B	HFO+HFC blend	466	~9.5%	Residential ducted AC	R-410A
R-1234yf	HFO	<1	~6.2%	Auto A/C, chillers	R-134a
R-455A	HFO+HFC blend	148	~8.4%	Commercial refrigeration	R-404A, R-507
R-466A	HFC blend	733	None (A1!)	R-410A alternative	R-410A

R-32

Difluoromethane (CH₂F₂) · Pure single-component HFC · A2L Safety Class

R-32 Technical Properties
Chemical Name	Difluoromethane (CH₂F₂)
GWP (100-year)	675 vs R-410A at 2,088
ODP	Zero (no chlorine)
ASHRAE Safety Class	A2L — mildly flammable
LFL (ignition concentration)	14.4% by volume
Burning Velocity	<10 cm/s (slow burn)
Blend Type	PURE compound — NOT a blend
Temperature Glide	NONE (pure compound)
Charge Method	Vapor OR liquid (pure = no fractionation)
Compressor Oil	R-32 SPECIFIC POE oil (not same as R-410A)
Operating Pressure vs R-410A	Slightly HIGHER than R-410A
Discharge Temperature vs R-454B	12-18°C (22-32°F) HOTTER
Cooling Capacity vs R-454B	~13% MORE capacity
Units in service globally	280 million+ (as of 2024)

              KEY EXAM FACTS: R-32
              R-32 is a PURE compound (single component) — it has NO temperature glide and NO fractionation risk.
              Because it is pure, it can be charged as vapor OR liquid.
              This makes it easier to top off in the field than zeotropic blends like R-454B.
            

              R-32 Discharge Temperature Warning
              R-32 runs 12-18°C HOTTER discharge temperature than R-454B.
              In hot climates, this requires compressor protection features.
              This is a primary reason some manufacturers chose R-454B for certain applications.
            

Most widely adopted A2L globally — dominant in ductless mini-splits
Major brands: Mitsubishi, Daikin, Fujitsu use R-32 in mini-splits
Requires R-32-specific POE oil — NOT the same as R-410A POE
Standard EPA 608 Type II covers R-32 — no new federal cert required
Must use A2L-rated recovery and service equipment
Can be recovered and reused on-site (pure compound, no blend issues)

R-454B

Opteon XL41 (Chemours) / Puron Advance (Carrier) · R-32 + R-1234yf Blend · A2L Safety Class

R-454B Technical Properties
Composition	R-32 (68.9%) + R-1234yf (31.1%)
GWP (100-year)	466 — 78% lower than R-410A
ODP	Zero
ASHRAE Safety Class	A2L — mildly flammable
LFL (ignition concentration)	~9.5% by volume
Burning Velocity	<10 cm/s (slow burn)
Blend Type	ZEOTROPIC blend — has temperature glide
Temperature Glide	Small (~1-3°F) — minor practical impact
Charge Method	LIQUID ONLY — zeotropic blend!
Compressor Oil	POE-32 (SAME as R-410A) — easier transition
Operating Pressure vs R-410A	Slightly LOWER — very similar to R-410A
Discharge Temperature vs R-32	LOWER — better for compressor longevity
Brand Names	Opteon XL41, Puron Advance
EPA SNAP Status	Approved R-410A substitute

              KEY EXAM FACTS: R-454B
              R-454B is the PRIMARY R-410A replacement for new residential DUCTED systems (central AC).
              It is a ZEOTROPIC BLEND of R-32 and R-1234yf.
              MUST be charged as LIQUID ONLY to prevent fractionation.
            

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MUST Charge as Liquid Only! R-454B is zeotropic — R-32 (lower boiling point) exits the cylinder first if charged as vapor, leaving an incorrect blend behind. ALWAYS charge R-454B as liquid.

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Cannot Top Off! Unlike R-32 (pure compound), R-454B zeotropic blend means you cannot simply add more. If system is undercharged, you must recover all refrigerant and recharge with a full fresh charge.

Same POE-32 oil as R-410A — easier manufacturer transition
Pressures nearly identical to R-410A — minimal component redesign
Lower discharge temp than R-32 — better for hot climates
Carrier, Trane, Lennox, York, Goodman using R-454B for ducted systems

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R-32 vs R-454B — Why Two Different Refrigerants? Both replace R-410A, chosen based on different design priorities. R-454B dominates residential ducted AC (pressure similarity to R-410A). R-32 dominates mini-splits and international markets.

R-32 (Difluoromethane)

Pure single compound — NO fractionation risk
Can be charged as VAPOR or LIQUID
GWP: 675
LFL: 14.4% (harder to ignite)
~13% MORE cooling capacity than R-454B
Pressure slightly HIGHER than R-410A
Discharge temp 12-18°C HOTTER than R-454B
Requires R-32-specific POE oil
Can be topped off (pure compound)
Dominant in mini-splits / VRF globally
Can be recovered & reused on-site

Best for: Mini-splits, ductless systems, VRF, international HVAC

R-454B (Opteon XL41)

Zeotropic blend (R-32 + R-1234yf) — has slight glide
LIQUID ONLY charge — no exceptions
GWP: 466 (lower than R-32!)
LFL: ~9.5% (slightly easier to ignite)
~13% LESS capacity than R-32
Pressure nearly IDENTICAL to R-410A
Discharge temp LOWER than R-32 (better for compressors)
Uses SAME POE-32 oil as R-410A
Cannot top off — must recover & recharge
Dominant in US residential ducted AC
More R-410A component compatibility

Best for: Residential central AC, large split systems, commercial rooftops

Side-by-Side Comparison Table — Exam Ready

Property	R-32	R-454B	R-410A (legacy)
GWP	675	466	2,088
ODP	0	0	0
Safety Class	A2L	A2L	A1
Flammable?	Mildly (A2L)	Mildly (A2L)	No
Blend type	Pure HFC compound	Zeotropic blend	Near-azeotrope blend
Charge method	Vapor or liquid OK	LIQUID ONLY	Liquid preferred
Can top off?	Yes (pure compound)	No (must recover all & recharge)	Not recommended
Operating pressure vs R-410A	Slightly higher	Nearly identical	Reference
Discharge temp vs R-410A	12-18°C hotter	Similar to R-410A	Reference
Compressor oil	R-32 specific POE	Same POE-32 as R-410A	POE-32
New residential ban	Required as of Jan 1, 2025		Banned Jan 1, 2025

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A2L Safety: Mandatory New Practices Working on A2L systems without proper procedures can result in fire hazards, equipment damage, and EPA violations. These practices are tested on the 2025-2026 EPA 608 exam.

Ignition Source Elimination — Required

NO open flames within the work area during recovery or charging
No arc-producing tools (grinders, sparking electrical equipment) near open refrigerant circuits
No smoking in the work area
No hot work (brazing, soldering) until system is fully recovered AND nitrogen-purged (double-purge protocol)

            Double-Purge Protocol Before Brazing A2L Systems
            1. Recover all refrigerant

            2. Purge with nitrogen

            3. Evacuate

            4. Purge with nitrogen again (5 minutes minimum)

            5. Evacuate once more

            THEN proceed with brazing or cutting

Ventilation Requirements

Ensure adequate ventilation before opening any refrigerant circuit
Equipment rooms may require ventilation upgrades per ASHRAE 15
ASHRAE 15 and IBC require automatic leak detection with equipment shutoff OR enhanced ventilation in occupied spaces
If a leak is detected: ventilate the area FIRST, then locate and repair
Mechanical rooms need CFM recalculation for A2L occupancy limits

Leak Detection — A2L Specific Rules

Must use A2L-RATED electronic leak detectors
Sensitivity must be at least 5 g/year (0.1 oz/year)
Detector must NOT produce sparks or heat above refrigerant auto-ignition temperature
Look for detectors explicitly labeled "A2L rated" or listing R-32, R-454B
ASHRAE 15 requires automatic refrigerant monitors in equipment rooms with A2L systems

Recovery — A2L Requirements

Must use A2L-RATED recovery equipment
Standard A1-only machines may not be certified for A2L
A2L recovery machines are typically dual-rated for A1 refrigerants too (one tool covers both)
Verify the SPECIFIC model is A2L certified — same model name does not mean same certification
Store recovery cylinders away from ignition sources
Label cylinders clearly — NEVER mix R-32 and R-454B
Same DOT cylinder rules: gray body, yellow collar, 80% max fill

Certification Requirements for A2L Work

EPA 608 Type II is sufficient
            Standard EPA 608 Type II certification covers A2L refrigerants under federal law.
            No new federal certification category is required as of 2026.

A2L Training Strongly Recommended
            A2L-specific safety training (4-8 hours) is required by many employers and some state jurisdictions.
            Covers safe handling, emergency procedures, and double-purge protocol.
            HVAC Excellence, ESCO, and NATE offer A2L endorsements.

AIM Act HFC Phasedown & Equipment Transition Timeline

Date	Event	Impact on Technicians
2022-2023	HFC production capped at 90% of baseline	R-410A prices begin rising
2024	HFC production drops to 60% — R-410A supply tightens sharply	Stock up or start transitioning
Jan 1, 2025	R-410A banned in NEW residential HVAC equipment	All new residential AC = R-454B or R-32
Jan 1, 2026	All new residential & light commercial must use compliant refrigerants	Full residential/light commercial transition
2028	Commercial equipment must use compliant refrigerants	Supermarkets, rooftops transition
2029-2033	HFC production at 30% of baseline	Very limited R-410A availability
2036+	HFC production at 15% of baseline (final target)	Minimal HFC refrigerant available

AIM Act key number: 85% HFC reduction by 2036. Production started declining 2022. R-410A new residential ban = January 1, 2025. Commercial transition = 2028.

Existing R-410A Systems — What You Need to Know

NO requirement to replace working R-410A equipment
R-410A can still service existing systems indefinitely
Do NOT mix R-410A with R-454B or R-32 in any system
New equipment installed after Jan 1, 2025 must use A2L refrigerant
R-410A supply will become increasingly limited and expensive

What You Cannot Do

Cannot put R-454B into an R-410A system
Cannot put R-410A into a new A2L-designed system
Cannot mix refrigerants in recovery cylinders
Cannot use old A1-only recovery equipment on A2L refrigerants
Cannot ignore A2L flammability precautions — EPA violations apply

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Core Section

25 questions · 18 correct to pass (72%) · Required for ALL certification types

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Most Failed Section Core tests exact legal language — specific dates, penalty amounts, and precise definitions. Know every word.

Key Dates — Memorize Every One

Date	Event
July 1, 1992	Unlawful to vent Class I (CFC) refrigerants
November 15, 1993	New recovery equipment must meet EPA certification standards
November 14, 1994	Technician certification required; venting Class II (HCFC) prohibited
January 1, 1996	CFC production ends in USA
November 15, 1995	HFCs added to venting prohibition
January 1, 2010	R-22 banned in new equipment
January 1, 2020	R-22 production and import ends completely
January 1, 2025	R-410A banned in new residential equipment (AIM Act)
January 1, 2026	All new residential & light commercial must use A2L refrigerants

1992=CFC venting ban. 1994=HCFC ban+cert required. 1996=CFC production ends. 2010=R-22 new equip ban. 2020=R-22 production ends. 2025=R-410A new equip ban.

Civil Penalties

$44,539 per day per violation (maximum) Periodically adjusted for inflation. BOTH technician and employer can each be penalized separately.

Venting regulated refrigerants
Servicing without certification
Failing to keep required records
Selling refrigerant to uncertified technicians
Purchasing containers over 2 lbs without certification

Certification Required?

REQUIRED:

Anyone servicing, repairing, or disposing of refrigerant equipment
Anyone purchasing refrigerant in containers over 2 lbs

NOT REQUIRED:

MVAC technicians (covered by Section 609)
Apprentices under direct supervision
Purchasing small cans under 2 lbs

Refrigerant Families — ODP & GWP

Family	Cl?	ODP	GWP	Status
CFCs (R-11, R-12)	Yes	High (1.0)	High	Banned 1996
HCFCs (R-22, R-123)	Yes	Low-Mod	Moderate	Phasing out
HFCs (R-410A, R-32)	No	ZERO	High-Very High	AIM phasedown
HFOs/A2L (R-454B)	No	ZERO	Near-zero to low	Growing

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Exam trap: HFCs (including R-32) have ZERO ODP but significant GWP. They don't destroy ozone but ARE greenhouse gases. R-32 GWP=675, R-454B GWP=466.

ODP vs GWP

ODP = Ozone Depletion Potential R-11 = 1.0 (reference standard). Measures ability to destroy stratospheric ozone. CHLORINE causes it. HFCs and HFOs = 0 ODP (no chlorine).

GWP = Global Warming Potential CO2 = 1 (reference). Measures greenhouse effect over 100 years. R-410A=2,088. R-32=675. R-454B=466. R-1234yf<1. AIM Act driven entirely by GWP.

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MOST TESTED CONCEPT on entire exam. Know every word of each definition exactly as written.

1. Recovery

Remove from system → external container. No processing required.

Refrigerant in any condition (dirty, mixed, vapor/liquid)
No purity testing required
Done on-site by certified technician
Cannot go into a new system without further processing

2. Recycling

Clean for reuse in SAME OWNER's equipment. On-site.

Oil separator and filter-drier used
Reuse in same system or same owner's other system only
Does NOT meet AHRI 700 standard
CANNOT be sold to another party

3. Reclamation

Process to AHRI 700 at EPA-certified facility. Can be sold.

Must meet AHRI Standard 700 — equivalent to virgin refrigerant
ONLY at EPA-certified reclamation facility
Reclaimed refrigerant CAN be sold to anyone
Purity documentation must accompany the refrigerant

Recovery = Remove it. Recycling = Clean it for yourself. Reclamation = Purify to AHRI 700 to sell it.

ASHRAE Safety Classifications

Class	Toxicity	Flammability	Examples
A1	Low	None	R-22, R-134a, R-410A, R-11, R-12
A2L	Low	Mildly flammable	R-32, R-454B, R-1234yf
A3	Low	Highly flammable	R-290 (Propane), R-600a (Isobutane)
B1	Higher	None	R-123
B2	Higher	Flammable	R-717 (Ammonia)

Recovery Cylinder Rules

Color: Gray body, yellow collar/top
DOT-approved pressure vessels only
Never fill above 80% of water capacity
Test date within 5 years
Must be labeled with refrigerant type
NEVER mix different refrigerants
Disposable cylinders CANNOT be refilled

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NEVER use oxygen for pressure testing. Oxygen + refrigerant oil = explosive. Use dry nitrogen ONLY.

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Type I — Small Appliances

25 questions · 21 correct to pass (84%) · Factory-sealed ≤5 lbs refrigerant

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Type I Definition: Equipment manufactured, charged, AND hermetically sealed at the FACTORY with 5 pounds or less of refrigerant. Window AC, household refrigerators, dehumidifiers, vending machines with ≤5 lb charge.

Recovery Methods & Requirements

System-Dependent (Passive): Use appliance own compressor. Recover until 0 psig. Requires working compressor.

Self-Contained (Active): External recovery machine. Required when compressor is non-working.

Equipment Date	Condition	Required Level
Pre-Nov 1993	Non-working compressor	80% OR 4" Hg vacuum
Post-Nov 1993	Non-working compressor	90% OR 4" Hg vacuum
Any date	Working compressor (passive)	Recover to 0 psig

Common Type I Refrigerants

Refrigerant	Application	Status
R-12	Old fridges (<1994)	Banned 1996
R-134a	Current fridges	Phasing down
R-22	Older window AC	Prod ended 2020
R-410A	Newer window AC	Banned new equip 2025
R-600a	New efficient fridges	Growing (A3 class)

Disposal Rules

MUST recover refrigerant before scrapping — always
Certified technician must remove refrigerant
Scrap recyclers must verify refrigerant removed
Records kept 3 years

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Never send refrigerant-containing equipment to a landfill without first recovering refrigerant.

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Type II — High-Pressure Systems

25 questions · 18 correct (72%) · R-410A, R-22, R-454B, R-32, R-134a, R-404A

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A2L Update for Type II: Exam now includes R-454B and R-32 questions. Know: R-454B = liquid charge only, R-32 = pure compound/vapor or liquid OK, both need A2L-rated equipment. See A2L tab for full detail.

Required Evacuation Levels — Type II

System Charge Size	Pre-11/15/93 Equipment	Post-11/15/93 Equipment
Less than 200 lbs	0 inches Hg vacuum	0 inches Hg vacuum
200 lbs or more	4 inches Hg vacuum	4 inches Hg vacuum

Type II: Under 200 lbs = 0" Hg. Over 200 lbs = 4" Hg. Type III (low-pressure) = 25 mm Hg absolute (completely different units & much deeper vacuum).

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THREE-TIER LEAK SYSTEM — Most Tested Type II Topic Know all three thresholds, the 30-day window, and the 60-day extension option.

Annual Leak Rate Thresholds (Systems with 50+ lbs of refrigerant)

Equipment Category	Max Annual Leak Rate	Repair Deadline
Comfort Cooling (HVAC)	10% per year	30 days
Commercial Refrigeration (50+ lbs)	20% per year	30 days
Industrial Process Refrigeration	30% per year	30 days

10-20-30: Comfort cooling = strictest (people live there). Commercial = middle. Industrial = most lenient. All = 30-day repair window.

Cannot repair in 30 days: apply for one-time 60-day extension from EPA
Not going to repair: must retrofit or retire within 12 months
Leak records must be kept 3 years
Applies ONLY to systems with 50+ lbs of refrigerant

Superheat (Cap Tube / Fixed Orifice Systems)

Superheat = T(suction line) - T(saturation at suction pressure) Low SH <5F = Overcharged or flooding High SH >20F = Undercharged or restriction

Subcooling (TXV Systems)

Subcooling = T(saturation at liquid pressure) - T(liquid line) High SC >20F = Overcharged Low SC <5F = Undercharged or restriction

Troubleshooting Quick Reference

Symptom	Likely Cause
High discharge pressure, non-condensables suspected	Air/nitrogen in system — recover and recharge
Low suction, low discharge	Undercharge / leak
Frost on suction line back to compressor	Overcharge or TXV stuck open
R-454B system low performance after service	Was R-454B charged as vapor? Must be liquid ONLY!
R-32 system runs hotter than expected	Normal — R-32 runs 12-18C hotter discharge than R-410A

R-454B — Primary New Residential Standard (2025+)

GWP: 466 | ODP: 0 | Safety: A2L
Blend: R-32 (68.9%) + R-1234yf (31.1%)
MUST charge as liquid (zeotropic blend)
Uses POE-32 oil (same as R-410A)
Pressures very similar to R-410A
Brand names: Opteon XL41, Puron Advance
Requires A2L-rated recovery equipment

R-32 — Dominant in Mini-Splits (2025+)

GWP: 675 | ODP: 0 | Safety: A2L
Pure compound — NO temperature glide
Can charge as vapor or liquid (pure compound)
Requires R-32-SPECIFIC POE oil (not same as R-410A)
Slightly higher pressure than R-410A
12-18°C higher discharge temp than R-454B

R-410A (Legacy — Being Replaced)

GWP: 2,088 | ODP: 0 | Safety: A1 (non-flammable)
Banned in NEW residential equipment Jan 1, 2025
Still legal to service EXISTING R-410A equipment
Uses POE-32 oil — incompatible with mineral oil
Operates at 1.6x higher pressure than R-22

R-22 (Legacy HCFC)

GWP: 1,810 | ODP: 0.055 | Safety: A1
BANNED in new equipment: January 1, 2010
ALL production ended: January 1, 2020
Reclaimed R-22 is STILL legal for existing systems
Uses mineral oil or alkylbenzene oil

R-22: 2010=new equip ban, 2020=production ends. Reclaimed=still OK for servicing.

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Type III — Low-Pressure Systems

25 questions · 18 correct (72%) · Centrifugal chillers · R-11, R-113, R-123

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Type III: Equipment operating at BELOW atmospheric pressure (vacuum) on low side. Large centrifugal chillers. Air leaks IN rather than refrigerant leaking out.

Evacuation Requirement — Type III

25 mm Hg absolute (≈29 inches Hg vacuum) — required regardless of recovery equipment date (same pre and post 1993).

Type III = 25 mm Hg absolute. Type II = 0 or 4" Hg vacuum. Type I working compressor = 0 psig. Three types, three different standards.

Type III Refrigerants

Refrigerant	ODP	Safety	Status
R-11 (CFC)	1.0	A1	Banned 1996
R-113 (CFC)	0.8	A1	Banned 1996
R-123 (HCFC)	0.012	B1 (higher tox)	Phasing out

⚠️

R-123 is B1 — higher toxicity! ASHRAE 15 requires a refrigerant ROOM MONITOR where R-123 is used.

Purge Units

Required because system operates in vacuum — air leaks IN
Removes non-condensables (air, moisture) while recovering refrigerant
High-efficiency units: ≤0.5 lbs refrigerant per lb of air removed
Non-condensables collect at TOP of condenser
Purge unit records must be maintained

Type II vs Type III Quick Comparison

Factor	Type II (High-Pressure)	Type III (Low-Pressure)
Low-side operating pressure	Positive (above atm)	Vacuum (below atm)
Leak direction	Refrigerant OUT	Air IN
Purge unit needed?	No	Yes — required
Evacuation units	Inches Hg vacuum (0 or 4)	mm Hg absolute (25)
Refrigerants	R-22, R-410A, R-454B, R-32	R-11, R-113, R-123

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Refrigerant Reference Guide

Complete properties for every refrigerant on the exam — including R-32 and R-454B

Refrigerant	Type	GWP	Safety	LFL	Oil	Replaces	Charge Method
R-32	Pure HFC	675	A2L	14.4%	R-32 SPECIFIC POE	R-410A (mini-splits)	Vapor or liquid
R-454B	HFO+HFC blend	466	A2L	~9.5%	POE-32 (same as R-410A)	R-410A (ducted)	LIQUID ONLY
R-1234yf	HFO	<1	A2L	~6.2%	PAG/POE	R-134a (auto A/C)	Liquid preferred
R-455A	HFO+HFC blend	148	A2L	~8.4%	POE	R-404A, R-507	Liquid only
R-466A	HFC blend	733	A1	None	POE	R-410A (non-flammable alt)	Liquid preferred

R-32 Key Facts

Pure compound — can charge vapor or liquid
GWP 675 — 68% lower than R-410A
12-18C higher discharge temp than R-454B
Requires R-32 specific POE oil
Dominant in mini-splits worldwide

R-454B Key Facts

Zeotropic blend — LIQUID charge ONLY
GWP 466 — 78% lower than R-410A
Uses same POE-32 oil as R-410A
Pressures nearly identical to R-410A
Primary US residential ducted AC replacement

Refrigerant	Components	GWP	Safety	Oil	Application	Status
R-134a	Pure HFC	1,430	A1	POE	Fridges, auto A/C, chillers	Phasing down
R-410A	R-32+R-125 (50/50)	2,088	A1	POE-32	Residential AC (legacy)	Banned new equip 2025
R-404A	R-125/R-143a/R-134a	3,922	A1	POE	Commercial refrigeration	Phasing down
R-407C	R-32/R-125/R-134a	1,774	A1	POE	R-22 retrofit alternative	Limited use
R-507	R-125+R-143a (50/50)	3,985	A1	POE	Commercial refrigeration	Phasing down

R-404A GWP=3,922 (highest common HFC). R-410A=2,088. R-134a=1,430. HFCs: ZERO ODP but HIGH GWP.

Refrigerant	Type	ODP	GWP	Safety	Status	Application
R-11	CFC	1.0 (reference)	4,750	A1	Banned 1996	Old low-P chillers
R-12	CFC	1.0	10,900	A1	Banned 1996	Old fridges, auto A/C
R-113	CFC	0.8	6,130	A1	Banned 1996	Low-P chillers
R-22	HCFC	0.055	1,810	A1	Prod ended 2020	Residential AC (legacy)
R-123	HCFC	0.012	77	B1	Phasing out	Low-P chillers (replaces R-11)

R-717 (Ammonia)

ODP: 0, GWP: 0 — environmentally ideal
Safety class: B2 — TOXIC, flammable
25 ppm OSHA PEL (dangerous at 300 ppm)
Most efficient natural refrigerant
Cannot use copper piping
Industrial refrigeration, food processing

R-744 (CO2)

ODP: 0, GWP: 1 (the reference!)
Safety class: A1
Very high pressures — up to 1,450 psig transcritical
Supermarkets, heat pumps, beverages

Hydrocarbons (A3)

R-290 (Propane): GWP=3, A3 — HIGHLY flammable
R-600a (Isobutane): GWP=3, A3 — household fridges
Charge limited to ~150 grams by flammability
NEVER near open flames or sparks

Azeotropic vs Zeotropic Blends — EXAM CRITICAL

Azeotropic Blends Behave like single pure substance. Single boiling point. No fractionation. Can charge vapor or liquid. Example: R-507 (near-azeotrope).

Zeotropic Blends — LIQUID Charge ONLY Components have different boiling points. CAN fractionate if charged as vapor. Always charge as liquid. Examples: R-454B, R-404A, R-407C, R-455A.

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R-454B is zeotropic — liquid charge ONLY. R-32 is a pure compound — can charge vapor or liquid. This distinction is tested on the exam.

Refrigerant	Type	Fractionation Risk?	Charge Method
R-32	Pure HFC	None (pure compound)	Vapor or liquid OK
R-454B	Zeotropic blend	YES — fractionates if vapor	LIQUID ONLY
R-410A	Near-azeotrope	Minimal (but liquid preferred)	Liquid preferred
R-404A	Zeotropic blend	YES	Liquid only
R-407C	Zeotropic blend	YES	Liquid only

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Formulas & Reference Charts

PT chart, conversions, superheat/subcooling, evacuation reference

Pressure Conversions

1 atm = 14.696 psi = 29.92 in Hg = 101.325 kPa psig = psia - 14.7 | psia = psig + 14.7 1 in Hg = 25,400 microns 500 microns = good deep vacuum (after evacuation)

Temperature Conversions

F to C: (F - 32) x 5/9 C to F: (C x 9/5) + 32 -40F = -40C (same in both scales!) Absolute zero = -459.67F = -273.15C

Superheat & Subcooling

Superheat = T(suction line) - T(sat at suction P) Subcooling = T(sat at liquid P) - T(liquid line) Normal SH (cap tube): 8-15F Normal SC (TXV): 10-20F

Pressure-Temperature Reference Chart (psig at saturation)

Temp F	R-22	R-134a	R-410A	R-404A	R-32 (approx)	R-123 (in Hg vac)
0F	11.8	6.0	101.6	97.4	~115	-28.4"
20F	21.1	17.1	165.3	159.2	~190	-27.4"
40F	35.0	29.5	236.7	228.4	~275	-25.8"
70F	62.6	57.1	382.5	372.1	~450	-21.5"
100F	117.2	105.0	629.3	612.5	~750	-13.2"
120F	163.7	148.9	831.2	813.1	~1000	-4.3"

R-32 runs slightly higher pressure than R-410A. R-454B pressures very similar to R-410A. R-123 operates in vacuum (negative inches Hg). Always use manufacturer PT charts for precise values.

Master Evacuation Requirements Chart

Type	Condition	Required Level
Type I	Working compressor (passive)	0 psig
Type I	Non-working compressor, pre-1993 equip	80% OR 4" Hg
Type I	Non-working compressor, post-1993 equip	90% OR 4" Hg
Type II	Less than 200 lbs	0 inches Hg vacuum
Type II	200 lbs or more	4 inches Hg vacuum
Type III	All sizes, any equipment date	25 mm Hg absolute (~29" Hg vac)

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Flashcards

Tap any card to reveal the answer — includes full R-32 & R-454B coverage

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EPA 608 Practice Exams

5 unique 100-question Universal exams · R-32 & R-454B included · 180-minute timed

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2025-2026 Updated Exam Bank All 5 tests include questions on R-32, R-454B, A2L safety, AIM Act phasedown, and the January 2025 R-410A ban. Each test rotates from 120+ question pool.

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Practice Test 1

Foundation · All sections
100 questions · 180 min

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Practice Test 2

Regulations Focus
Heavy Core & Law

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Practice Test 3

Technical Focus
Refrigerants & Systems

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Practice Test 4

A2L & AIM Act Focus
R-32 & R-454B heavy

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Practice Test 5

Advanced Challenge
Hardest questions

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Glossary

Every term including R-32, R-454B, A2L, and AIM Act — searchable