Often confused · Refrigerants and oils
A2L refrigerants: what the A, the 2 and the L mean
An A2L refrigerant is one rated lower toxicity (the A) and lower flammability (the 2L) under ASHRAE Standard 34, with R-32 the best-known example; per ESCO, the revised EPA 608 exam adds general-knowledge questions on A2Ls (ACHR News, September 19, 2026).
Part of Refrigerants and oils in the Study guide
Reading a safety class: letter, then number
- A
- Lower toxicity. Most comfort-cooling and commercial refrigerants are in this group.
- B
- Higher toxicity. R-123, the low-pressure chiller refrigerant, is the B the 608 exam knows best: ASHRAE 15 calls for a refrigerant-specific sensor in R-123 equipment rooms.
- 1
- No flame propagation in the standard test.
- 2L
- Lower flammability: hard to ignite and slow-burning, but able to burn. The L is a subclass of 2.
- 2
- Flammable, above the 2L subclass.
- 3
- Higher flammability. Hydrocarbons belong here.
Where common refrigerants sit
ASHRAE 34 safety class of refrigerants named in EPA 608 study material
| Refrigerant | Type | Safety class | Where you see it |
|---|---|---|---|
| R-410A | HFC blend | A1 | Residential AC and heat pumps installed before the transition |
| R-32 | HFC | A2L | Newer residential and light-commercial AC |
| R-454B | HFC/HFO blend | A2L | Newer residential and light-commercial AC |
| R-1234yf | HFO | A2L | Mostly motor-vehicle AC, which is Section 609 territory |
| R-290 | Hydrocarbon (propane) | A3 | Only the end-uses EPA lists for it |
| R-123 | HCFC | B1 | Low-pressure chillers on the Type III section |
Safety classes are ASHRAE Standard 34 designations, set by ASHRAE; they aren't an EPA rule. ESCO hasn't published which A2L details the revised exam tests.
What is and isn't on the EPA 608 exam
A2L coverage in the old and new question banks
| Item | 2018 bank | 2026 bank |
|---|---|---|
| A2L and A3 general knowledge | Not in the EPA test topics | Added, per ESCO |
| Structure | Core plus Type I, II, III; Universal is all four | Same; no separate A2L certification type |
| AIM Act rules | Not tested | Not tested, per ESCO |
Yellow edge: the two columns say different things on this row.
EPA test topics: last updated December 5, 2025 (EPA test topics, checked October 7, 2026). New-bank details: ESCO Institute as reported by ACHR News on September 19, 2026 (checked October 7, 2026); treat that column as medium confidence. Cutover dates and editions are on the new EPA 608 exam page.
Letters, numbers and handling
Decode the safety class first, then decide what it changes about the job in the stem.
0 right · 0 of 8 answered
Which of the following is an example of a non-flammable substance commonly found in refrigeration systems?
Why each option is right or wrong
Answer: C. Water
- AWrong: isobutane (R-600a) is a hydrocarbon refrigerant and is highly flammable (safety class A3).
- BWrong: butane is a hydrocarbon and highly flammable.
- CCorrect: water is non-flammable; in a refrigeration system it shows up mainly as a contaminant.
- DWrong: propane (R-290) is a hydrocarbon refrigerant and highly flammable (safety class A3).
Water is a non-flammable substance that can be found in refrigeration systems, typically as an unwanted contaminant. In contrast, propane, butane, and isobutane are examples of flammable substances that must be handled with caution in specific applications.
A manager requests replacing R-410A with R-32. Technicians must remember some low-GWP alternatives are mildly flammable (A2L) and verify the substitute refrigerant's safety classification. What is the primary regulatory risk of overlooking safety-class differences here?
Why each option is right or wrong
Answer: A. R-32 is an A2L and cannot be retrofitted into legacy systems strictly designed for A1 refrigerants.
- ACorrect: R-32 is an A2L, and SNAP accepts it only in new equipment designed for it, not as a retrofit into systems built for A1 refrigerants.
- BWrong: R-32 runs at pressures similar to or slightly higher than R-410A, not lower.
- CWrong: R-32 is A2L, which means lower toxicity, not a toxic Class B refrigerant.
- DWrong: R-32 is used with POE oil; it doesn't react with it to form sludge.
R-410A is an A1 (non-flammable) refrigerant, while R-32 is mildly flammable (A2L). A2L refrigerants cannot be dropped into legacy equipment designed solely for A1 safety classifications.
When transitioning to mildly flammable substitutes, technicians must apply appropriate safety protocols, ventilation, leak-detection, and use service equipment rated for flammable refrigerants. Which additional precaution is critical?
Why each option is right or wrong
Answer: A. Grounding recovery machines
- ACorrect: grounding recovery equipment helps prevent static or electrical sparks near a flammable refrigerant.
- BWrong: oxygen must never be used in a refrigeration system and would be dangerous with a flammable refrigerant.
- CWrong: disposable cylinders must never be used to hold recovered refrigerant.
- DWrong: equipment must be rated for flammable refrigerants; standard equipment may create ignition sources.
Grounding the recovery machine prevents static sparks, a real ignition risk with a mildly flammable refrigerant. Equipment rated for flammable refrigerants, ventilation and leak detection come first; grounding is the step added on top.
A technician is preparing to braze a high-pressure system charged with an A2L substitute refrigerant. To comply with safety protocols, what is the correct sequence of preparatory steps before applying heat?
Why each option is right or wrong
Answer: A. Recover the gas, purge with nitrogen, ensure ventilation, and confirm the area is below the LFL
- ACorrect: recover the refrigerant, purge with nitrogen, ventilate, and confirm the area is below the lower flammability limit (LFL) before brazing.
- BWrong: purging before recovery pushes the refrigerant out into the room, which is venting and a fire risk.
- CWrong: pushing the gas out with air vents it and adds oxygen to the system.
- DWrong: skipping the nitrogen purge leaves flammable refrigerant in the lines when the torch is applied.
Before brazing an A2L system, recover the refrigerant, purge with nitrogen, ensure adequate ventilation, and confirm with a detector that the refrigerant concentration is well below its lower flammability limit (LFL).
What specific characteristic makes a refrigerant classified as Class A?
Why each option is right or wrong
Answer: C. Lower toxicity with permissible exposure limit of 400 ppm or greater
- AWrong: higher toxicity is Class B, not Class A.
- BWrong: flammability is rated by the number (1, 2L, 2, 3), not the letter A.
- CCorrect: Class A means lower toxicity, with an occupational exposure limit of 400 ppm or more.
- DWrong: pressure has nothing to do with the toxicity letter.
Class A refrigerants have lower toxicity with a permissible exposure limit of 400 ppm or greater.
Which hydrocarbon (HC) refrigerant is permitted for use in new commercial refrigeration equipment?
Why each option is right or wrong
Answer: D. R-290
- AWrong: R-404A is an HFC blend, not a hydrocarbon.
- BWrong: R-717 is ammonia, not a hydrocarbon.
- CWrong: R-407C is an HFC blend, not a hydrocarbon.
- DCorrect: R-290 (propane) is a hydrocarbon that is acceptable in some new commercial equipment, such as stand-alone units.
R-290 (propane) is listed as acceptable under EPA's SNAP program for several new commercial refrigeration uses, within charge-size limits. R-717 is ammonia, not a hydrocarbon, and R-404A and R-407C are HFC blends.
Which pair contains two refrigerants that are both in ASHRAE safety group A2L?
Why each option is right or wrong
Answer: A. R-32 and R-454B
- ACorrect: both R-32 and R-454B are lower-toxicity, lower-flammability A2L refrigerants.
- BR-134a is in group A1, so only R-32 in this pair is A2L.
- CR-410A is in group A1 (nonflammable), so this pair does not qualify.
- DR-290 (propane) is in group A3, higher flammability, not A2L.
R-32 and R-454B are the A2L refrigerants most often used to replace R-410A in new equipment. R-410A and R-134a are A1, and hydrocarbons such as R-290 are A3.
In the ASHRAE 34 safety classification A2L, what do the "A" and the "2L" stand for?
Why each option is right or wrong
Answer: D. A = lower toxicity; 2L = lower flammability
- AThe letter rates toxicity, not flammability, and nothing in the class describes GWP.
- BThe letter A means lower toxicity; higher toxicity is marked with the letter B.
- CHigher flammability is class 3; 2L is the lowest flammable subclass.
- DCorrect: A is lower toxicity and 2L is lower flammability, a class 2 subclass with a low burning velocity.
In ASHRAE 34 the letter rates toxicity (A lower, B higher) and the number rates flammability: 1 no flame propagation, 2L lower flammability, 2 flammable, 3 higher flammability. The 2L subclass covers refrigerants with a burning velocity of 10 cm/s or less.
More practice across all four sections: Practice test · Timed mock
Your 608 card already covers A2L systems
A2L isn't a separate certification that replaces Section 608. Per ESCO (ACHR News, September 19, 2026), the revised exam keeps the four-section format and folds A2L questions into it, and cards already issued stay valid. Separate A2L safety courses exist and are voluntary; the EPA 608 vs A2L training comparison lays out what each one covers.
Pressure class is a separate exam idea from safety class, set by saturation pressure at 104 °F (40 CFR 82.152, eCFR as of October 5, 2026). The parent topic, refrigerants and oils, places A2Ls among the other substitutes.
Sources
- What You Need to Know About the New Section 608 Exam — published September 19, 2026; checked October 7, 2026ACHR News, quoting ESCO Institute
- Section 608 Test Topics — last updated December 5, 2025; checked October 7, 2026U.S. EPA
- Prohibition on Venting Refrigerants — checked October 7, 2026U.S. EPA