2025 is a major transition year for the HVAC industry and heat pumps, due to refrigerants transitioning from high GWP A1 refrigerants to lower GWP A2L refrigerants. This transition carries many long-awaited improvements and advantages for distributed refrigerant systems such as mini-splits, multi-splits and larger VRV/VRF systems. This transition also requires updates and changes to local building codes, including the Massachusetts 10th Edition Building Code, an effort led by HTS and DXS with the BBRS. This session will provide an overview of the system design and application impacts of these new A2L refrigerants for distributed refrigerant systems (under ASHRAE 15 2022 and the 10th Edition Building Code). We will also discuss the pros and cons of distributed A2L refrigerants versus packaged systems with hydronic distribution. Lastly, this session will address refrigerant leakage and related emissions from these systems, and the impacts of the added components for A2Ls, such as refrigerant detectors and automatic refrigerant isolation valves.