New York City has officially adopted new rules governing the use of A2L refrigerants in building systems. Signed by DOB Commissioner Ahmed Tigani on April 7, 2026, the rule takes effect immediately for all new refrigerating systems installed after that date. For developers and architects, particularly those working on projects that use Variable Refrigerant Flow (VRF) systems, these changes have significant design and coordination implications.
Background: Why These Rules Exist
A2L refrigerants – including R-32 and R-454B – are the next-generation alternatives to R-410A, which is being phased out under the EPA’s Hydrofluorocarbon (HFC) phasedown program. While A2L refrigerants have a dramatically lower Global Warming Potential (GWP), they are classified as mildly flammable. That characteristic is what drives the new safety requirements.
Rather than adopting the 2024 edition of ASHRAE 15, which would have simplified some requirements (such as allowing a vented shaft exception), NYC chose to retain ASHRAE 15-2022 as its baseline and layer on a set of NYC-specific rules. The result is a more stringent local framework.
Key Requirements – Especially for VRF
The following are the most consequential changes for projects using VRF or other direct-expansion systems with A2L refrigerants:
Refrigerant Detection with FDNY Alarm Integration
All A2L systems require an integral refrigerant detection system. This is built into new VRF equipment, but the NYC rule goes further: the detection system must generate three distinct output signals integrated with the building’s FDNY fire alarm system:
- FDNY Alarm (Emergency): Triggered when refrigerant concentration reaches 25% of the Lower Flammability Limit (LFL). Must respond within 30 seconds and automatically de-energize compressors, pumps, and ignition sources.
- FDNY Fault (Trouble): Triggered when concentration reaches the Occupational Exposure Limit (OEL). Initiates Level 1 ventilation.
- FDNY Supervisory: Triggered when the detector identifies a malfunctioning system component.
This three-signal integration needs to be coordinated with the project’s fire alarm engineer early in design.
Effective Dispersal Volume (EDV) Calculations for All Spaces VRF Piping Passes Through
One of the more demanding requirements: EDV calculations are required for every occupied space through which VRF refrigerant piping passes – not just the spaces served by the system. This expands the scope of refrigerant charge analysis considerably on multi-floor or corridor-routing scenarios.
Pipe-in-Pipe Construction in Public Corridors and Across Floor Slabs
A2L refrigerant piping routed through public corridors or penetrating floor slabs must be enclosed in pipe-in-pipe construction (an outer sleeve of the same pipe material) AND further enclosed within construction with a 2-hour fire-resistance rating. This has real implications for routing strategy: piping through tenant demising walls or private spaces may be acceptable, but running through public corridors adds cost and complexity.
No Vented Shaft Exception – Dedicated Shafts Remain Required
Unlike ASHRAE 15-2024, the NYC rule does not include the vented shaft exception. Dedicated, vented refrigerant shafts are still required when piping must travel vertically through a building. This is a significant point for high-rise or multi-story mixed-use projects.
Pressure Testing Witnessed by Special Inspector
Refrigerant pressure testing (per ASHRAE 15 Sections 9.13 and 9.14) must be witnessed by a special inspector. Special inspections should be included in the project’s inspection program from the outset.
Design Strategy Recommendations
For amenity and base-building spaces, the most effective strategy to manage complexity is to position outdoor condensing units as close as possible to the indoor fan coil units they serve. Shorter piping runs mean lower refrigerant charges, fewer spaces requiring EDV calculations, and reduced exposure to corridor-routing restrictions. Avoiding public corridors altogether – where feasible – eliminates the pipe-in-pipe requirement entirely.
For residential applications, the rules are also significant. ASHRAE 15 (as modified) applies to R-1 and R-2 occupancies, with ASHRAE 15.2 covering R-3 single-family and two-family dwellings. Multifamily buildings can comply using unitary systems or central hydronic systems, which avoids the need for field-installed refrigerant detection.
What This Means for Project Teams
These rules apply to all A2L refrigerating systems installed after April 7, 2026. Projects that received DOB plan approval and have equipment ordered under the prior framework should confirm their compliance path with their mechanical engineer.
For new projects entering design, early coordination between the mechanical engineer, fire alarm designer, and the architect on refrigerant piping routing is essential – particularly on projects where VRF is being considered for amenity spaces, base building, or residential units.
EP Engineering is actively working with project teams to navigate these requirements. If you’d like to discuss how the new rules apply to a specific project, please reach out.
For additional information, visit:
- NYC DOB Final Rule – Refrigerant Safety Standards (adopted April 7, 2026)
- EP Knows: EPA Hydrofluorocarbon (HFC) Phasedown – What Does This Mean for VRF?
- EP Knows: 2025 Energy Code Update