A2L refrigerant
A2L · mildly flammable refrigerant · lower flammability refrigerant
An A2L refrigerant is one classed under ASHRAE Standard 34 as lower toxicity (A) and lower flammability with slow flame propagation (2L); R-454B and R-32 are examples.
ASHRAE Standard 34 gives each refrigerant a letter for toxicity and a number for flammability. Class A is lower toxicity, class B higher. Class 1 does not propagate a flame. Class 2L has lower flammability and slow flame propagation, for example a burning velocity under 10 cm/s. Classes 2 and 3 are more flammable.
Many lower-GWP refrigerants are A2L. EPA’s examples include R-32, R-452B, R-454B, R-1234yf and R-1234ze. EPA notes that A2L refrigerants will not ignite below their lower flammability limit, but because they can propagate a flame, precautions are needed to prevent a build-up, especially in enclosed spaces.
EPA’s SNAP listings for A2L refrigerants require compliance with UL Standard 60335-2-40, Edition 3. In practice, A2L equipment is designed around its refrigerant and installed and serviced by technicians trained for it. R-410A, which it replaces in new home systems, is class A1.
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