A3 refrigerant leak detection—the next step after A2L

The introduction of A2L refrigerant detection systems in North America contributed significantly to Sensirion’s revenue growth in 2025. In parallel, we have been developing A3 refrigerant sensing solutions for next generation heat pumps and air conditioning units following low GWP requirements in Europe and Asia.

Following an integrated strategy from technology leader ship to customer intimacy, Sensirion has established market leadership for refrigerant leakage sensors in the transition to A2L refrigerants in the United States. Building on this success, we are ready to tackle the next major shift in the heating, ventilation, air-conditioning (HVAC) indus try: the transition to natural refrigerants in Europe and Asia. While A2L refrigerants are only mildly flammable, A3 refrigerants are highly flammable and reliable leak detec tion is a key technical enabler for a safe use of these environ- mentally friendly, economical and efficient refrigerants.

Regulations and trends in Europe and Asia 

Heat pumps play a key role in substituting fossil fuels by renewable energies in heating systems worldwide, and thus in decarbonization and energy independence. In warm climate zones, air conditioning (AC) systems are a main driver for electricity consumption. Traditionally, heat pumps and AC units rely on hydrofluorocarbons (HFCs) as refrigerants. These synthetic greenhouse gases have a very high global warming potential (GWP), thousands of times higher than CO2. Different local regulations mandate the transition from HFCs to low-GWP alternatives in the current decade, similar to the introduction of A2L refriger ants in North America in 2025. While A2L refrigerants have a relatively low global warming potential (GWP), these fluorinated substances (PFAS) raise increasing concerns and the European Union has adopted strict regulations that strongly favor the use of natural refrigerants, such as propane (R-290). In addition, China has also recently issued guidelines to accelerate this transition and promote the introduction of natural refrigerants in the coming years. Other countries will follow suit.

Propane (R-290) as a climate-friendly refrigerant 

Natural, non-fluorinated, refrigerants are required to further reduce the climate impact of these systems and enable truly sustainable HVAC solutions. Propane has excellent thermodynamic properties, making systems using R-290 highly energy efficient. It also has a low GWP, occurs naturally and is inexpensive as well as non-toxic. However, propane is highly flammable and is therefore classified in the safety group A3 according to ASHRAE safety classifi cations. To mitigate the potential safety risk, a refrigerant leakage detection sensor is required in some applications. We expect a rapid expansion in the global use of propane as a refrigerant and, consequently, an increase in demand for leakage detection sensors. In the short to mid term, the primary markets are expected to be Europe and Asia, while A2L refrigerants will continue to be used in North America.

Sensirion’s opportunities 

We strongly believe that the increasing use of the environ mentally friendly refrigerant R-290 will create significant opportunities for Sensirion’s A3 refrigerant leakage solu tions, and the first products are already on the market today. By building on the close relationship with the major global HVAC manufacturers and the integrated value chain devel oped in the A2L campaign, together with the technological leadership in gas sensing technology, we are well prepared for the increase in demand in the coming years.

We introduce Bryan Zhang and Gianluca Bartolomeo, Sensirion’s experts in A3 leakage detection sensing. Bryan works as Senior Market Manager for the HVAC Sales Team and is the direct contact person for our key customers. Gianluca works as Product Manager for gas sensors and defines the sensor solutions together with our Research & Development engineers.

A3 as the next step after A2L for Sensirion. What does that mean? 

Bryan Zhang: A2L was a major revenue driver in 2025 and, through strong market adoption, we established market leadership in A2L refrigerant leakage sensors in North America. However, A3 is not a replacement for A2L. A2L will remain the solution for refrigerant leakage detection in the US and Canada. 

Gianluca Bartolomeo: Rather, A3 represents another major growth opportunity for Sensirion. In the coming years, sensors for A3 refrigerant leakage detection will be in demand in Europe and Asia as propane will be establishing itself as an environmentally friendly refrigerant on both continents. Combining Sensirion’s technological excellence with close collaboration with key customers in the development of our solutions, we are very well positioned to meet the increasing demand and achieve market leadership.

For what applications will sensors for detecting A3 refrigerant leakage be used? 

Bryan: The switch to refrigerants with lower global warming potential is imminent in various countries around the world. These refrigerants are often highly flammable. Whether for regulatory reasons or as safety features, the demand for sensors that detect leaks quickly, effectively and reliably will increase. 

Gianluca: A3 refrigerants will be used in a wide range of HVACR applications, from heat pumps and large residential systems to smaller and even portable AC units.

What sensor solutions does Sensirion offer? 

Gianluca: Our sensors are based on a technology platform that has already been proven and established itself on the market in other products such as our CO2 sensors, namely the photoacoustic measurement principle. The development of the sensing core has been successfully completed.

Bryan: Depending on our customers’ needs, we offer different sensor solutions, as we do with A2L: a sensing core for customization and integration for high-volume applications, and customized modules for the specific requirements of appliances. We will also offer a standard module through our distribution channels.

What are the advantages of having close contact with the key players in the HVACR market? 

Bryan: We are involved in our customers’ development projects right from the very beginning. This close collabora tion gives us a deep understanding of the applications as well as the needs and requirements for our sensor solution. We can offer our customers added value and a better expe rience, even for their end customers. 

Gianluca: We provide our customers with safe, reliable and cost-effective solutions. Through close collaboration, we are shaping not only the next generation of our sensor solutions but also the next generation of our customers’ products, which makes me very proud.

What are the challenges of the A3 campaign? 

Gianluca: On the technical side, it was challenging to develop and launch an A3 sensing core so quickly, consid ering the very tough requirements in terms of reliability. 

Bryan: The A3 campaign for the heat pump market is chal lenging as the market is highly fragmented. By introducing a standard module and leveraging our distribution chan nels, we are able to serve a wide range of customers across multiple countries.

Any final thoughts? 

Gianluca: I would like to thank all our colleagues involved in the A3 campaign, from Marketing & Sales to Research & Development and Operations & Production. It was a great experience, and we are only at the beginning! 

Bryan: The work was carried out with great ambition, passion and dedication. The cooperation is exceptional. Thank you very much and let’s keep the momentum!