The zero ozone-depleting potential (ODP) of hydrofluorocarbon (HFC) refrigerants has been the major driver for their widespread adoption in heating, ventilation, air conditioning and refrigeration (HVAC&R) products in recent years. However, many HFCs have relatively high global warming potential (GWP), which has driven industry to evaluate low-GWP alternative refrigerants. Nearly all refrigerants currently in widespread use are nonflammable, classified A1 by ANSI/ASHRAE Standard 34, but many viable low-GWP refrigerants, including certain HFCs and hydrofluoroolefins (HFO), are flammable. ANSI/ASHRAE Standard 34-2013 includes a new flammability classification, A2L, specifically for non-toxic refrigerants with low burning velocity. A2L refrigerants have less dangerous flammability characteristics than A2 and A3 refrigerants. A3 hydrocarbon (HC) refrigerants, such as propane (R-290) and isobutane (R-600a), are also being introduced in some applications due to their zero ODP and low GWP. Development of safety codes and standards to mitigate flammability risks is essential to ensuring safety of consumers, service technicians, and building occupants.

The objectives of this project were to:

• Characterize current international and domestic best practices for safe use of flammable refrigerants across various end-uses and building sectors.
• Characterize current US practices and potential gaps in standards for the use of flammable refrigerants.
• Leverage this research to recommend guidelines for flammable refrigerants in the U.S.
• Recommend appropriate testing to validate these guidelines.