A2L · Low GWP · R-454B · R-32

Pass the A2L certification exam. Then charge R-454B by the numbers.

300+ original practice questions across the eleven A2L / Low GWP safety topics, a 50-question mock exam with explanations, and the field calculators you keep after the test: superheat and subcooling with glide handled correctly, and the room-based max charge check. Free, offline, no account.

Free
iPhone & iPad
Works offline
No account

Try ten questions first: free A2L practice test in your browser.

Practice mode

Study like the exam. Learn from every miss.

Many distributors and manufacturers now ask for an A2L / Low GWP refrigerant safety card before they will sell you equipment. Practice mode drills the material the exam covers, in the format the exam uses.

300+ original questions, eleven topics. A2L characteristics and ASHRAE 34 classes, flammability metrics and GWP, codes and regulations, A2L tools, handling and transport, leak detection and mitigation, recovery and evacuation, servicing and charging, installation and charge limits, emergency procedures, retrofit and transition.
Quick 10, topic drills, and a 50-question mock exam. Optional 35-minute timer. Score by topic, review every miss, retake in one tap.
An explanation for every answer. Math questions are solved by the same engine as the calculators, so the numbers are correct by construction and the worked solution shows each step.
Progress stays on your phone. Lifetime accuracy, weakest topic, recent sessions. No account. The app sends anonymous usage stats (which screens get used, never your answers or inputs), and you can switch that off in Settings.
Honest about what a score means. Above or below 70% is shown for orientation. Your test provider’s passing score governs, and a practice score is not a certification.

In the field

Practice, then charge.

A2L Certification Test Prep practice question about R-454B dew point with the correct answer highlighted and an explanation — Every question explains the answer, whether you got it right or not.

Calculating R-454B superheat from suction pressure and line temperature — Superheat and subcooling update as pressure and temperature are entered.

Maximum allowable R-454B charge calculation using room area and wall-mounted equipment — Check the nameplate against the room-based charge limit and show every assumption.

Field tools you keep after the exam

Making the jump from R-410A? So is everyone.

Built for residential HVAC techs, apprentices, and HVACR students moving to R-454B and R-32. The new refrigerants need different PT references, glide handling, and room safety math than what you have been running for a decade.

Superheat and subcooling in seconds. Enter suction or liquid pressure in psig and line temp in °F. Get the actual number with typical-range context and an optional OEM target comparison.
Glide handled right. R-454B superheat uses dew point, subcooling uses bubble point, automatically. The app will not let you mix them up.
Nameplate check against the room limit. Length, width, mount location, and nameplate charge in. A clear Within / Exceeds result with margin and the m1 / m2 / m3 charge tier out, for floor, wall, or ceiling units.
Active mitigation toggle. Systems with listed leak detection and response controls get the expanded limit. The passive number stays on screen for reference.
PT tables built in. R-454B, R-32, and R-410A data ship inside the app. Basements, mechanical rooms, rooftops. Zero bars, full function.
A2L quick reference. Refrigerant comparison, safety rules, and a bubble-and-dew explainer. The cheat sheet stays in your pocket.
PDF job tickets. Export any calc as a one-page PDF with your company name, tech name, license number, and an optional GPS stamp. Generated entirely on the device.
History that writes the ticket. Every calc auto-saves with a timestamp and optional job label. Pull it back up at the truck.

The numbers behind the numbers

Sourced data, shown sources.

Max charge formula: structured per UL 60335-2-40 / ASHRAE Standard 15.2, with the attribution shown on every result and PDF.
Flammability limits: LFL values from ASHRAE 34-2022 (R-454B 0.303 kg/m³, R-32 0.307 kg/m³), with installation heights for floor, wall, and ceiling mounts.
Charge tiers: m1 / m2 / m3 gates computed from LFL per UL 60335-2-40 Annex GG.
PT data sources shown on every result: Chemours Opteon XL41 (NIST REFPROP 10.0) for R-454B, Daikin / Hudson Technologies (NIST) for R-32, National Refrigerants Reference Guide 7th Ed. for R-410A.
Practice questions: original material written for the app; every number in a question is drawn from the same constants the calculators use, and each question carries a source pointer for review.
Honest results: typical ranges are shown for context, never pass-fail badges, and every result carries a disclaimer. It is a study aid and a calculation aid, not a certification or a substitute for the OEM charging procedure or code compliance review. The OEM plate overrides field bands.

Common questions

A2L certification prep and charging FAQ

Is this the official ESCO Low GWP exam?

No. A2L Certification Test Prep is an independent study tool with original practice questions. It is not affiliated with, endorsed by, or approved by ESCO Institute, Mainstream Engineering, the U.S. EPA, or any certifying body. The ESCO Low GWP Refrigerant Safety exam is a 50-question closed-book test; Mainstream Engineering offers an open-book version. Both cover the same material the app drills.

What topics does the practice exam cover?

Eleven topics: A2L characteristics and ASHRAE 34 classes, flammability metrics and GWP, codes and regulations (AIM Act, EPA 608, UL 60335-2-40, ASHRAE 15/15.2), A2L tools, handling and transport, leak detection and mitigation, recovery and evacuation, servicing and charging, installation and charge limits, emergency procedures, and retrofit and transition.

How do you calculate R-454B superheat?

Enter suction pressure (psig) and suction line temperature (°F). For R-454B, superheat uses dew-point saturation temperature. The app selects dew point automatically so you do not mix bubble and dew.

Do you use bubble or dew point for R-454B?

Use dew-point saturation temperature for superheat and bubble-point saturation temperature for subcooling. The app selects the correct value automatically.

How is A2L max charge calculated?

Enter room length, width, and mount location (floor, wall, or ceiling). The app estimates maximum allowable charge using methods structured per UL 60335-2-40 and ASHRAE Standard 15.2, with an active-mitigation option when leak detection and response controls are present. OEM nameplate and local code still override field estimates.

Does the app work offline?

Yes. The practice question bank and the pressure-temperature data for R-454B, R-32, and R-410A are stored in the app, so studying and calculating both work without an internet connection.

Get it offline

Free. Study on the truck, charge in the basement.

Install once. Practice questions and PT tables never leave the device.

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