Question: why are some hfo refrigerants classified as a2l?
Answer: Because of their lower GWP values, these refrigerants have a much shorter life cycle in the atmosphere. These two HFO refrigerants have an A2L safety classification meaning they have low toxicity but are slightly flammable (See Table 2 here). ... HFO-1234yf has a GWP that's 300 times less than that of HFC-134a.