AHRI Flammable Refrigerants Research Initiative

The HVAC&R industry is transitioning to low GWP refrigerants due to environmental concerns and regulatory requirements . Many of these low GWP refrigerants are classified as lower flammability which has required the update of relevant safety standards and codes to implement these environmentally friendly refrigerants in the field in a timely and cost-effective manner.

Relevant safety standards updates have been underway for many years. The standard revision and code adoption processes are relatively slow while regulations are advancing quickly. This is, in part, because of a lack of publicly available knowledge about the safe use of these refrigerants. To address this challenge, US industry, HVACR society, federal and local governments have collaboratively conducted research to understand the refrigerant flammability and the safe use of these refrigerants for several years. The Air-Conditioning, Heating and Refrigeration Institute (AHRI) has been leading a research program aimed at generating publicly available and sound technical data to support code and standard activities related to the use of flammable refrigerants. This $ 6 million plus program was jointly funded by AHRI, ASHRAE, California Air Resource Board and US Department of Energy. The goal of the research initiative is to deliver scientific findings and produce publicly available technical references to support code and standard activities related to the use of flammable refrigerants.

Underwriters Laboratory and the American Society of Heating and Refrigeration Engineers (ASHRAE) along with stakeholders including industry experts have worked to update the safety standards. AHRI surveyed 46 relevant safety standards’ committees and WGs related to flammable refrigerants for technical data gaps. High priority projects were identified and initiated to understand the refrigerants flammability risk, refrigerant charge quantity, refrigerant detector technologies, mitigation effectiveness and equipment installation. The project reports have been shared with the standard communities and the public and has been used to substantiate changes to safety standards. The list of these projects is attached in Exhibit-1.

The industry is taking a systematic and conservative approach to ensure safe use of flammable refrigerants with a great amount of effort to understand the potential risk. Several whole room-scale refrigerant leak and ignition tests were conducted for air-conditioning and refrigeration products beyond the worst case scenarios with the events unlikely happening by using multiple strong ignition sources placed in locations where combustible mixtures were most likely to occur. In addition, the rapid liquid refrigerant release used in testing is an extremely low-probability type of leak. The testing suggested that, if used, refrigerant detection systems would need a faster response time than the 30 second response originally envisioned by the safety standards. This detection response time change has been adopted by the relevant safety standards such as ASHRAE Standard 15 and UL 60335-2-40. Additional experimental investigation on potential ignition sources inside domestic residence demonstrated that many household ignition sources cannot ignite mildly flammable refrigerants such as burning cigarette, sparks from common household appliances and tools etc.

The industry is continuing its work to further assess the use of mildly flammable refrigerants to inform the continuous upgrading of the safety standards and to confirm previous learnings by other industries already using mildly flammable refrigerants.

Exhibit-1: The following launched projects were developed as the result of the survey of safety standard community. They were prioritized among other identified research needs and considered as high priority projects by a group of experts including industry experts, major safety standard committee chairmen and members, and representatives from U.S. Department of Energy (DOE), Environmental Protection Agency (EPA) and National Institute of Standards and Technology (NIST).

Launched High Priority Projects

Funding Organization

Project Description


AHRTI-9007-01: Benchmarking Risk by Whole Room Scale Leaks and Ignitions Testing of A2L Refrigerants


A2L refrigerants leak and ignition testing under whole room scale conditions was conducted to develop data and insight into the risks associated with the use of A2L refrigerants versus A1 refrigerants while considering ambient conditions (temperature and humidity) and refrigerant lubricants.


AHRTI-9007-02: Benchmarking Risk by Whole Room Scale Leaks and Ignitions Testing of A3 Refrigerant


This project is to conduct A3 refrigerant leaks and ignitions testing under whole room scale conditions, understand the risk associated with the use of A3 refrigerants, and provide test data to support future revisions of relevant safety standards associated with using A3 refrigerants.


AHRTI-9008: Investigation of Hot Surface Ignition Temperature for A2L Refrigerants


The objective of this work is to develop a test methodology to assist in the evaluation of the propensity of A2L refrigerants (R32, R1234ze, and R452B) to ignite on hot surfaces, and to carry out testing per the new test methodology.


AHRTI-9009: Leak Detection of A2L Refrigerants in HVACR Equipment


A thorough review of sensor technologies was conducted to evaluate available technologies that can be used to meet safety standards requirements of detecting A2L refrigerants and easily integrated into air-conditioning and refrigeration equipment. Infrared (IR) and Metal Oxide Semiconductor (MOS) sensors were found to be the most promising sensor technologies.


AHRTI-9014: Assess Refrigerant Detector Characteristics for Use in HVACR Equipment


The objective of the project is to assess refrigerant sensor and refrigerant detector performance requirements for class 2L, 2, 3 flammable refrigerants for use with indoor HVACR equipment, whether in an occupied space or a machinery room.


AHRTI-9015: Assessment of Refrigerant Leakage Mitigation Effectiveness for Air-Conditioning and Refrigeration Equipment


The objective of this project is to demonstrate the efficacy of refrigerant leakage mitigation strategies contained within residential split-systems, packaged air-conditioning equipment and commercial refrigeration products.


ASHRAE-1806: Flammable Refrigerants Post-ignition Risk Assessment


The objective of this project is to understand the Severity of events where flammable refrigerants are ignited under different scenarios for various HVAC&R products.


AHRAE-1807: Guidelines for flammable refrigerant handling, transporting, storing and equipment servicing and installation


This project accessed flammable refrigerant safety guidelines and/or requirements that exist domestically and internationally. The assessment will be used to propose requirements/guidelines for the safe handling, storing and transporting of flammable refrigerants.


ASHRAE-1808: Servicing and Installing Equipment Using Flammable Refrigerants: Assessment of Field-made Mechanical Joints


This project tested the leak-tightness of various types of field-made joints used to connect refrigerant piping and system components in HVAC&R equipment. The results of this project provided necessary data to suggest whether or not common types of joints, other than brazed or soldered joints, should be permissible for use in equipment containing flammable refrigerants.


AHRAE-1855: Determination of the Impact of Combustion byproducts on the Safe Use of Flammable Fluorinated Refrigerants


The overall objective of the project is to understand the HF and COF2 exposure risk if ignitions of flammable halogenated refrigerants occur and how to clean up following a variety of ignition events, as well as to identify knowledge gaps.


ORNL: Determination of setting charge limits for various types of equipment employing flammable refrigerants


The primary objective of the project is to examine the currently imposed limits for flammable refrigerant alternatives (A2L, A2, and A3) and identify reasonable adjustments to these limits as appropriate.


ORNL: Experimental Evaluation of Refrigerant Leak Characteristics for Different HVAC&R Equipment Types


The objective of the project was to quantify actual leak rates and duration for various pieces of equipment by conducting refrigerant leak tests under operating conditions representative of actual applications.


NIST: Modeling Tools for Flammability Ranking of Low-GWP Refrigerant Blends


The project is to develop modeling tools that can predict the burning velocity of arbitrary mixtures of R32, R125, R134a, R152a, 1234yf, and 1234ze(E), so that flammability of a blend can be minimized, while simultaneously maximizing performance related to other parameters.