The stratosphere holds ~90% of Earth's ozone, shielding the surface from UV-B radiation. CFCs and HCFCs contain chlorine that reaches the stratosphere and destroys ozone. Each chlorine atom can destroy up to 100,000 ozone molecules (Rowland-Molina theory). The 1987 Montreal Protocol established global CFC/HCFC phaseout schedules.

• ODP (Ozone Depletion Potential) — measured relative to R-11 = 1.0
• GWP (Global Warming Potential) — measured relative to CO₂ = 1.0, over 100 years
• Class I = ODP >0.2 (all CFCs — phased out 1996)
• Class II = ODP <0.2 (all HCFCs — R-22 banned 2020)

Intentionally venting any regulated refrigerant is illegal — including HFCs with zero ODP. Only four types of releases are permitted:

• De minimis releases from good-faith hose connection/disconnection
• Refrigerant emitted during normal equipment operation (not during servicing)
• Nitrogen + trace system refrigerant used as leak-check gas (only after evacuation)
• Exempt refrigerants: CO₂, R-600a, R-290, nitrogen, water

• Exam answer: $44,539 per day per violation (40 CFR §82.169)
• CAA max (Jan 2025): $124,426 per day per violation
• Reporting reward: up to $10,000
• Both employer AND technician can be penalized for the same violation
• EPA can revoke certification

• Must record: date, type of service, equipment location, equipment owner, normal charge, refrigerant added or removed
• Retain records minimum 3 years
• Failure to keep records = violation

• Only EPA 608-certified technicians may purchase refrigerant in containers >2 lbs
• Selling used refrigerant without reclamation is prohibited
• Homeowners servicing their own equipment are not subject to the technician certification requirement — but they still CANNOT purchase refrigerant in containers over 2 lbs without certification

A leak rate is the percentage of a system's total refrigerant charge that escapes in one year. EPA calculates it by dividing the amount of refrigerant added during the year by the full nameplate charge, then multiplying by 100. When a system's leak rate exceeds the threshold for its equipment type, the owner is legally required to repair the leak — not just top it off. Adding refrigerant to a leaking system without repairing it is a violation. Different equipment types have different thresholds because the environments they serve vary in how quickly a leak can be addressed.

ALD (Automatic Leak Detection) required at ≥1,500 lbs HFC charge (new installs within 30 days, existing installs by Jan 1, 2027)

Refrigerant oil circulates with the refrigerant throughout the system to lubricate the compressor. The oil must be miscible with the refrigerant — meaning the two mix together and stay mixed, like water and juice. If an oil is not miscible with the refrigerant, it separates out and forms droplets that coat the inside of the heat exchanger tubes, reducing efficiency, and eventually starve the compressor of lubrication causing catastrophic failure.

When a system is retrofitted from an older refrigerant (like R-22) to a newer HFC or HFO refrigerant, the oil must be changed because the old mineral oil is not miscible with the new refrigerant. The system must be flushed until less than 5% of the old oil remains before the new POE oil is added. This is why EPA says there are no true "drop-in" replacements — even if pressures are similar, the oil change is always required.

• Azeotropic (500-series): Zero temperature glide — behave like pure refrigerant. Can charge as vapor or liquid. Can top off after a leak.
• Zeotropic / non-azeotropic (400-series): Temperature glide — must charge as LIQUID ONLY. Cannot top off — fractionation changes blend composition. Must recover all and recharge with fresh refrigerant.
• Near-azeotropic: Very small glide (e.g. R-410A ≈ 0.2°F) — treated like pure refrigerant in practice.

EPA's SNAP (Significant New Alternatives Policy) program evaluates substitute refrigerant safety. According to EPA, there are no true "drop-in" replacements — every retrofit requires some system modification. SNAP approval only means a refrigerant reduces overall risk to health and environment.

• Compressor: Pumps low-pressure vapor → high-pressure vapor
• Condenser: Rejects heat; high-pressure vapor → high-pressure liquid
• Expansion device (TXV/cap tube/orifice): Drops pressure; allows refrigerant to boil in evaporator
• Evaporator: Absorbs heat; low-pressure liquid/vapor → all vapor (provides cooling)
• Filter drier: Removes moisture and contaminants from liquid line
• Crankcase heater: Prevents refrigerant migration into compressor oil during off cycles

• Fully hermetic: Motor and compressor welded in single casing — no gaskets
• Semi-hermetic: Bolted gasketed sealing surfaces (serviceable)
• Open-drive: Rotating shaft seal — motor external to refrigerant

• High-pressure gauge (red) — measures discharge side pressure
• Compound low-pressure gauge (blue) — measures suction side; dual scale (psig + inches Hg vacuum)
• Center hose (yellow) — used for recovery, evacuation, or charging
• R-410A requires manifold rated ≥800 psig working / 4,000 psig burst

EPA (Environmental Protection Agency) requires service hoses on recovery/recycling equipment to use low-loss fittings. These close automatically or manually when disconnected, minimizing refrigerant releases.

• The ONLY accurate field method to verify deep vacuum
• Manifold compound gauge is not accurate below ~25,000 microns
• 500 microns = EPA minimum · 300 microns = industry best practice
• Connect gauge directly at the system — not near the vacuum pump

• Two-stage pump required for HVAC/R work (pulls below 500 microns)
• Gas ballast valve: open during initial evacuation, close when vacuum reaches 20–25 in. Hg
• If pump cannot reach <500 microns when isolated → oil is contaminated, change oil

Any time you open a refrigerant circuit — even just to replace a filter drier — you are legally required to recover the refrigerant first. You cannot open a system and let the refrigerant vent to atmosphere. Once recovered, what you do with that refrigerant depends on its condition and who owns the equipment it came from.

Recovery means removing the refrigerant from the system and storing it in a recovery cylinder. You do this before ANY repair, whether the system is being serviced or scrapped. No special equipment certification needed — just EPA-certified recovery equipment.

Recycling means running the recovered refrigerant through an oil separator and filter-drier on-site to clean it up for reuse. It's good enough to go back into the SAME system or another system owned by the same person — but you can't sell it or give it to someone else because it hasn't been purified to a documented standard.

Reclamation is the highest level — an EPA-certified off-site facility purifies the refrigerant back to new-product purity meeting AHRI Standard 700. Only reclaimed refrigerant can legally cross ownership. When a tech recovers refrigerant from a customer's system, they must either return it to that same customer's system or send it to a reclaimer — they can't take it and use it in someone else's equipment.

• Acidity: <0.01% · Moisture: <10 ppm · Non-condensable gas: <1.5%
• Nonvolatile residue: <100 ppm · Chloride content: none

• Self-contained: Has its own compressor; works on any size system including broken compressors. Required if you hold any cert other than just Type I.
• System-dependent: Uses the system's compressor/pressure. Max 15 lbs refrigerant.

• Color: gray body + yellow top
• Max fill: 80% of capacity
• Hydrostatic retest: every 5 years
• One refrigerant type per cylinder — never mix
• Never use disposable cylinders for recovery

• 500 microns = EPA minimum evacuation level
• 300 microns = industry best practice
• 1,000–5,000 microns rising after pump isolation = moisture still present
• Above 5,000 microns rising = possible system leak
• Rises above 0 psig = refrigerant trapped in oil

• Evacuate to 1,500–2,000 microns
• Break vacuum with dry nitrogen — raise to 10–15 psig
• Vent nitrogen (exempt — no recovery needed)
• Repeat 3 times total
• Final pull to ≤500 microns; hold 10–15 min and verify holds

Air in system cannot condense — accumulates in condenser, raises head pressure, causes premature component failure. Also carries moisture that forms acids. Check by comparing measured pressure to P-T chart at known temperature — pressure higher than expected = non-condensables present.

• Electronic/ultrasonic detector: EPA says most effective for detecting general area of small leak. Sensitivity ~0.5 oz/year. Never expose probe to high refrigerant concentration.
• Soap bubble test: Good for small systems when all surfaces can be coated
• UV/fluorescent dye: Useful for small hard-to-find leaks; not immediate — dye must accumulate. Ineffective in bright sunlight.
• Pressure decay (standing pressure) test: Best to VERIFY system is leak-free. Pressurize with dry nitrogen to nameplate pressure, monitor for drop over time.

• Flush system with approved non-aqueous flushing solution (not the compressor, filter drier, or expansion device)
• Replace compressor, oil (switch to POE), and refrigerant
• Install both suction-line and liquid-line filter driers
• Never flush with refrigerant — illegal under current EPA regulations

After evacuation, introduce nitrogen to slightly above atmospheric pressure before opening the system. This prevents the vacuum from drawing air and moisture into the system when opened.

Most refrigerants are heavier than air, odorless, and invisible. When released they displace oxygen. Ensure ≥4 air changes per hour. Refrigerant vapor concentrates in low areas.

• Splash-proof safety glasses with side shields — always
• Protective gloves and footwear to prevent frostbite
• If refrigerant contacts skin or eyes: flush with water for ≥15 minutes
• SCBA required in large refrigerant release in confined space

• Never fill above 80% capacity
• Never apply open flame or live steam to any cylinder
• Transport upright and secured
• Hydrostatic test every 5 years
• Discard disposables: reduce to 0 psig, puncture or break valve, recycle metal

• Fill to ≤80% capacity · Hydrostatic test within 5 years · Cylinders upright and secured
• DOT classification tag on each cylinder · Shipping papers with proper name, hazard class, UN number, 24-hr emergency phone

Factory-sealed, fully manufactured, hermetically sealed with 5 lbs or less of refrigerant. Examples: household refrigerators, window ACs, dehumidifiers, vending machines, water coolers, under-counter ice makers.

• System-dependent: Uses appliance compressor/pressure. Max 15 lbs. For passive recovery with broken compressor, connect BOTH high and low sides.
• Self-contained: Has own compressor. Works on broken systems. If you hold any cert other than just Type I, must have at least one on-site.

• Sealed copper tube = one-time access point on hermetically sealed appliances
• Pierce with piercing-type (saddle) access valve
• After service: crimp upstream of valve → remove valve → braze shut. Never leave valve in place — it will leak.
• Flammable HC systems: use fittings specifically rated for flammable refrigerants only

• Identify refrigerant (nameplate or P-T chart)
• Connect recovery equipment to DOT-approved cylinder (same refrigerant type)
• Allow natural pressure-driven flow first, then start recovery machine
• After repair + new filter drier: static pressure decay leak test
• Evacuate to ≥500 microns (triple evacuation recommended)
• Recharge with recovered refrigerant (same system/owner) or new/reclaimed refrigerant

• Red tubing: Required at all service ports and process tubes — minimum 1 inch in both directions from each service location
• Red marking must always be present — replace if removed or shortened during service
• DANGER and CAUTION labels permanently attached at: evaporator, machine compartment (×2), refrigerant tubing, exterior of appliance
• All flammable refrigerant containers: red band on shoulder or top

• Ground the refrigeration system, recovery unit, AND recovery cylinder — eliminates static spark risk
• Check area for flammable liquids/vapors before starting work
• Never use EPDM, natural rubber, or silicone rubber components in HC/HFO systems
• Never use lubricants with silicone/silicate additives
• Only use recovery equipment expressly certified for that flammable refrigerant

• A2L = mildly flammable, max burn velocity ≤10 cm/s
• Examples: R-454B, R-32, R-1234yf, R-452B
• R-454B = primary R-410A replacement in new residential equipment (GWP = 466, ~78% lower than R-410A)
• Requires A2L-rated equipment — standard R-410A tools NOT acceptable
• Red tubing marking required at all service locations
• Ground system, recovery unit, and cylinder during recovery

• Liquid recovery is faster than vapor
• Use larger diameter hoses (⅜" or ½" for larger systems)
• Remove unnecessary Schrader valve core depressors
• Heat the system (raises system pressure)
• Cool the recovery cylinder (lowers cylinder pressure, increases pressure differential)

• Activate crankcase heater (releases refrigerant dissolved in oil)
• Strike compressor with rubber mallet to dislodge trapped refrigerant
• For frost-free refrigerators: activate defrost heater to raise vapor pressure
• Connect BOTH high and low sides for passive recovery

• Two ports preferred — faster, ensures complete recovery
• Required for passive recovery with broken compressor
• One port acceptable for small appliances due to small charge
• With working system compressor + one port: recover from HIGH side so compressor pumps refrigerant there

• Burnout refrigerant (highly acidic): must reclaim — cannot reuse or recycle
• Mixed refrigerants: send to certified reclaimer or EPA-approved destruction facility
• Refrigerant with non-condensables: must reclaim
• When in doubt: don't use the refrigerant

• Recovery required before ANY disposal — even to landfill
• No certification required to recover for disposal only
• Final person in disposal chain (e.g. scrap dealer) is responsible and must maintain records

Type II covers any system that is NOT a small appliance (over 5 lbs of refrigerant) AND not a low-pressure chiller. This is the most common certification — it covers residential split systems, rooftop units, heat pumps, and commercial refrigeration. The key skill Type II tests is knowing which pressure class a refrigerant belongs to, because the required recovery level depends entirely on that classification.

Refrigerants are grouped by their saturation pressure at 104°F. This determines recovery requirements and what tools are safe to use. Never use equipment rated for a lower-pressure refrigerant on a higher-pressure one — the equipment can fail catastrophically.

R-22 was the dominant HVAC refrigerant for decades. It's an HCFC — it contains chlorine which depletes the ozone layer. New production was banned January 1, 2020. Only reclaimed or recovered R-22 can now be used to service existing equipment. R-22 is a high-pressure refrigerant — it runs at about 69 psig at 40°F saturation, uses mineral oil, and requires high-pressure rated tools.

• ODP = 0.034 · GWP = 1,700 · ASHRAE A1 · Light green cylinder
• No new production since Jan 1, 2020 — reclaimed stock only
• No true drop-in replacement — every retrofit requires oil change to POE
• Common replacements: R-407C, R-422D, R-438A, R-448A

R-410A replaced R-22 in new residential equipment starting in the early 2000s. It's an HFC blend with zero ODP — no chlorine. However its GWP of 2,088 made it a target of the AIM Act. New residential equipment using R-410A was banned January 1, 2025. Existing R-410A systems can still be serviced — R-410A is not banned from use, just from new equipment manufacturing.

• ODP = 0 · GWP = 2,088 · ASHRAE A1 · Rose/pink cylinder
• Very high pressure — 118 psig at 40°F saturation
• Requires POE oil only — never mineral oil
• New residential equipment ban: Jan 1, 2025
• Recovery to 0 psig (atmospheric) — never pull vacuum on R-410A

R-454B (marketed as Opteon XL41) is the primary replacement for R-410A in new residential HVAC equipment from 2025 onward. It's an HFO/HFC blend with a GWP of just 466 — about 78% lower than R-410A. The tradeoff is that R-454B is A2L (mildly flammable), which requires new tools, equipment, and service procedures.

• ODP = 0 · GWP = 466 · ASHRAE A2L · Very high pressure
• Requires A2L-rated recovery equipment — standard R-410A tools NOT acceptable
• Red tubing marking required at all service locations (minimum 1 inch)
• Ground system, recovery unit, AND cylinder when recovering
• Max burn velocity ≤10 cm/s — mildly flammable, not highly flammable

These are the same rates from the Core section, but now they apply to the real equipment you'll be servicing. A 10-ton rooftop R-22 unit holds roughly 10–15 lbs of refrigerant. Under the AIM (American Innovation and Manufacturing) Act effective January 1, 2026, HFC systems with 15 lbs or more are now subject to leak rate obligations — meaning most commercial equipment you'll work on falls under these rules.

Most modern HFC refrigerants used in Type II systems are zeotropic blends — R-407C, R-404A, R-448A. These must always be charged as liquid. If a zeotropic system develops a large leak, you cannot simply top it off — the remaining refrigerant has fractionated and the blend composition is wrong. You must recover everything and recharge with fresh refrigerant.

• R-407C temperature glide ≈ 10°F — use bubble point for subcooling, dew point for superheat
• R-410A temperature glide ≈ 0.2°F — near-azeotropic, treated like pure refrigerant in practice
• R-404A temperature glide ≈ 1°F — charge as liquid only

• 25 Core questions + 25 Type II questions = 50 total
• Must pass both sections at 70% (18/25) independently
• Proctored closed-book only — no open-book option for Type II
• If Core was previously passed open-book for Type I: must retake Core proctored (but NOT the 25 Type I questions)

Type III is the most specialized certification. It covers large centrifugal chillers found in hospitals, universities, office towers, and hotels — equipment that can cool an entire building from a single machine. These systems are fundamentally different from everything else in refrigeration because they operate below atmospheric pressure (in a vacuum). Understanding why completely changes how you think about leaks, recovery, and service.

R-11 boils at +74.9°F at atmospheric pressure — basically room temperature. For R-11 to be useful as a refrigerant (producing cooling at, say, 44°F chilled water), the system must operate at pressures well below atmospheric. The evaporator on a centrifugal chiller running R-11 might be at 3–4 inches of mercury vacuum — less pressure than the outside air.

This creates the opposite problem from high-pressure systems. On a rooftop unit, a leak means refrigerant escapes outward. On a low-pressure chiller, a leak means outside air is drawn IN. The system is always fighting to keep air and moisture out, and it loses a little ground every day through gaskets and shaft seals — which is exactly why purge units exist.

A purge unit is a device unique to low-pressure chillers. Because outside air constantly seeps into the sub-atmospheric system through gaskets and seals, the purge unit runs continuously to separate and remove that air before it accumulates. It works by drawing a small sample of refrigerant-air mixture from the condenser, condensing out the refrigerant (which returns to the system), and venting the non-condensable air outside.

High-efficiency purge units are required by EPA because older purge units lost significant refrigerant along with the air they vented. Modern purge units recover nearly all the refrigerant before venting.

• Excessive purge operation = system is leaking more air than normal → find and repair the leak
• Excessive moisture in purge discharge = water-side tube leak (cooling water entering refrigerant side)
• Non-condensables accumulate in condenser = raise head pressure, reduce capacity, cause acid formation
• Purge unit logs must be maintained and available for EPA inspection
• Rupture disc on evaporator: blows at 15 psig to prevent over-pressurization

Low-pressure recovery uses a completely different pressure scale from high-pressure systems. Instead of inches of mercury vacuum, it's measured in millimeters of mercury absolute — a much deeper vacuum that requires specialized equipment.

• Start with liquid removal first — faster, more efficient
• Must circulate water through chiller tubes during recovery to prevent freezing
• ~100 lbs of R-11 vapor remains in a 350-ton chiller at 0 psig — must continue to 25 mm Hg
• Bring system to 16.9 inches Hg vacuum before introducing liquid R-11 during recharge
• Use dry nitrogen to bring system to atmospheric before opening for service

Because the system runs below atmospheric pressure, leak testing works differently. You cannot pressurize a low-pressure chiller to the same levels as a high-pressure system — the relief device would blow. Maximum leak test pressure is 10 psig with nitrogen, always staying below the 15 psig rupture disc pressure.

• R-123 AEL (Allowable Exposure Limit) = 30 ppm — the maximum airborne concentration considered safe for an 8-hour workday. Compare to R-11 AEL = 1,000 ppm. Requires active ventilation and refrigerant monitoring in the chiller room.
• R-123 decomposes to toxic products near open flame
• R-11 decomposes to phosgene and halogen acid gases near flame
• Never siphon refrigerant by mouth — basic safety, appears on exam
• Never add compressed air to a low-pressure system — introduces moisture and acids
• Use alcohol spray to remove ice from sight glass

• 25 Core questions + 25 Type III questions = 50 total
• Must pass both sections at 70% (18/25) independently
• Proctored closed-book only