A2L certification practice test: 10 free questions with answers

1. Characteristics

   What does the “2L” in an A2L safety classification tell you about the refrigerant?

   • It is lower flammability: it burns, but slowly and only within a narrow concentration range
   • It has a lower toxicity than an A1 refrigerant
   • It is a two-component blend with low glide
   • It contains less than 2% hydrocarbon by weight
   Answer

   A. In ASHRAE 34 the number is the flammability class and the letter is toxicity. Class 2L is the “lower flammability” subclass of Class 2: it propagates a flame but with a burning velocity of 10 cm/s or less.

2. Flammability

   Refrigerant detection systems for A2L equipment are required to respond no later than what fraction of the LFL?

   • 5%
   • 25%
   • 50%
   • 100%
   Answer

   B. Detection acts at 25% of LFL, leaving a four-fold safety margin before the mixture could burn. That margin absorbs sensor drift, uneven mixing, and pockets near the floor.

3. Codes

   Is it legal to intentionally vent R-32 or R-454B to the atmosphere during service?

   • Yes — they are not ozone-depleting
   • Yes, if the quantity is under 2 lb
   • No — the venting prohibition covers HFC and HFO substitutes as well as ODS refrigerants
   • Only outdoors
   Answer

   C. The Clean Air Act venting prohibition applies to substitute refrigerants (HFCs, HFOs, and their blends). De minimis releases during good-faith recovery are allowed; deliberate venting is not.

4. Tools

   May a recovery machine that is NOT rated for A2L refrigerants be used to recover R-32 if the work area is well ventilated?

   • Yes — ventilation makes it safe
   • Yes — R-32 is only mildly flammable
   • No — the ignition risk is inside the machine, so only A2L-rated equipment should be used
   • Yes, if the cylinder is A2L-rated
   Answer

   C. Room ventilation does nothing for vapor that accumulates inside a machine housing next to a brushed motor or relay. Use equipment listed for flammable refrigerants regardless of how well the room is ventilated.

5. Handling

   What thread direction do flammable-refrigerant cylinder valve outlets use under the U.S. industry cylinder guideline?

   • Right-hand (standard)
   • Left-hand (reverse)
   • Metric fine
   • Quick-connect only
   Answer

   B. Under AHRI Guideline N, cylinders for flammable refrigerants (including A2Ls) use left-hand threaded valve outlets so a hose from a non-flammable refrigerant will not fit without an adapter — a physical barrier to cross-charging and mixing.

6. Leak detection

   Where is the RDS sensor typically mounted on a residential A2L indoor coil or air handler?

   • At the top of the cabinet near the supply
   • Low in the cabinet, near the drain pan, where leaked refrigerant would collect
   • On the outdoor unit
   • In the return-air grille of the living room
   Answer

   B. Leaked A2L vapor is heavier than air and sinks. The sensor sits near the lowest point of the coil compartment so it sees the leak first.

7. Recovery

   What must be done before applying a torch to any part of an A2L refrigerant circuit?

   • Charge the system so the flame cannot enter the pipe
   • Recover the refrigerant, evacuate, and flow dry nitrogen through the circuit during brazing
   • Open all valves to atmosphere
   • Nothing extra — A2Ls are only mildly flammable
   Answer

   B. A torch on a circuit containing refrigerant vapor can ignite it at the joint and creates toxic decomposition products. Recover, evacuate, and purge with nitrogen — the standard sequence now has a life-safety reason on top of the metallurgical one.

8. Servicing

   When calculating superheat on an R-454B system, which saturation temperature is used?

   • Bubble point
   • Dew point
   • The average of bubble and dew
   • Discharge saturation
   Answer

   B. Superheat is measured on the vapor side, and a zeotrope finishes evaporating at its dew point. With roughly 1.5–3 °F of glide, using the bubble point would overstate superheat by that much.

9. Installation

   Two identical R-32 wall units are installed in a 100 ft² office and a 400 ft² living room. How do their passive charge limits compare?

   • The living room allows 4× the charge
   • The living room allows about 2× the charge, because the limit scales with the square root of area
   • They are equal — area does not matter for wall units
   • The office allows more because it is smaller
   Answer

   B. m_max ∝ √A. Quadrupling the area doubles the limit. This is why small bedrooms, not the whole house, drive A2L equipment selection.

10. Emergency

    Which action is WRONG during an A2L leak in a closed room?

    • Opening doors and windows
    • Flipping light switches on to see better
    • Shutting off refrigerant flow at the outdoor unit if it can be done safely
    • Keeping people out until the space is checked
    Answer

    B. A light switch can arc. In a room that may contain a flammable concentration, avoid operating any electrical switch — use a flashlight brought from outside, or leave the lights as they are.

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