Refrigerant gas detectors are used to detect leaks from refrigeration systems. That much is simple and obvious. When one scratches the surface of the subject, however, things become much more complex. There is a plethora of choices on the market that all offer a different range of benefits and are best applied to different applications or different goals.

In the 4^th century BC, the Ancient Greek philosopher, Aristotle, said:

“Excellence is never an accident. It is always the result of high intention, sincere effort, and intelligent execution; it represents the wise choice of many alternatives – choice, not chance, determines your destiny.”

Wading through the available selection of gas detection equipment is not straightforward for anybody who does not find themselves an expert in refrigerant gas detection – which is most of us. That said, if one follows the 2,400-year-old maxim from Aristotle, excellence can be achieved via the right intention, effort, and execution. Working in partnership with refrigerant detection experts, ones willing to share the expertise which comes from a daily focus on the subject, can be the key to unlocking the right refrigerant gas detection solution for any given site or application.

Identifying the goal

There are many different reasons why a refrigerant monitor can be needed.  For the owner or operator of a refrigeration system, identifying why they need to take action in the event of a refrigerant gas alarm is the first step in making the right choice. These can include:

Refrigerant Safety

• Refrigerant leaks pose serious hazards. While many refrigerants aren’t toxic at low levels, when present in high amounts, they can displace oxygen, leading to potential asphyxiation risks. Some refrigerants, in particular ammonia (NH₃), are toxic at much lower levels. Flammability is also a concern for both ammonia, propane (R290) refrigeration systems. This concern of flammability also includes A2L refrigerants which are growing in use globally driven by the phase-down of HFC gases (driven by, for example, F-Gas regulations in Europe and the AIM Act in the United States), because they typically have a lower global warming potential (GWP) than the older refrigerants they are superseding in the market.

Various global standards, such as EN 378 in the European Union and ASHRAE 15 in the United States, are implemented to ensure the safe operation of refrigeration systems. These standards encompass the entire installation process and include clauses specifying the proper utilization of refrigerant leak detectors, along with alarm systems, to promptly detect concentrations that surpass safe levels and initiate mitigation of the risks posed.

Environmental Impact

• The release of most commonly used fluorinated refrigerants, including HFCs (hydroflourocarbons) and HFOs (hydrofluoro-olefins) into the atmosphere carries significant environmental consequences, with Global Warming Potentials (GWPs) hundreds or even thousands of times higher than that of carbon dioxide (CO₂). In the battle against climate change, such emissions are highly undesirable and can impact significantly on the carbon footprint of the business from whose systems they are emitted.

Regulations, for example the Environmental Protection Agency’s (EPA) Clean Air Act Section 608 in the USA, and F-Gas in Europe, aim to curb uncontrolled emissions and enforce penalties and fines for refrigerant leaks that exceed specified thresholds.

Some members of the refrigeration industry are strong advocates of the use of what are commonly known as “natural” refrigerants, due to the presence of these gases being a natural part of Earth’s atmosphere and their significantly lower CO₂ equivalence in GWP terms meaning a lesser climate impact in the event of leaks. These include CO₂ (R744), NH₃ (R717), and propane (R290). Others contend that as the chemical-grade gases needed for refrigeration are manufactured, not harvested naturally, they still have a climate impact.

When factoring in safety and other concerns, wherever one finds oneself in the natural refrigerant debate, it is clear that refrigerant leaks are bad.

Energy Efficiency

• In a typical supermarket operation, refrigeration systems can consume up to 70% of the total energy used. A significant loss of refrigerant charge, say up to 15% from a slow but persistent leak, could see energy costs could spike by up to 50% in order to sustain system performance. Of course, this can vary somewhat depending on the size of type of system in use, but a similar scenario on any system would be significant in its impact. Such increases have substantial financial implications at a site level and are even more pronounced across larger enterprises.

Recent economic factors have exacerbated this concern. In the United Kingdom, for example, commercial electricity prices have increased by as much as 120% from the start of 2021 through to the end of 2023, according to government figures.

Effective deployment of a refrigerant gas monitoring system can allow a refrigerant leak to be detected, fixed, and the refrigerant in the system topped-up to optimise performance and energy efficiency.

Product loss / shrinkage

• Cooling is an essential part of the global food chain, ranging in its use from food production, transport, and distribution warehouse storage, through to supermarket cold rooms and retail display cases. Refrigerant leaks can result in cooling that does not meet the required food safety standards, or in the worst-case complete failure of the cooling system. In either case, the resulting food spoilage creates waste and has a deep economic impact. In the case of premium products such as dry-aged beef, or luxury ice cream, one unmitigated refrigerant leak could bear a cost running into tens of thousands of dollars. Comparative examples can be drawn in other sectors, for example in refrigerated pharmaceutical production and storage. These are costs that could be prevented through effective refrigerant leak detection.

The Rising Cost Of Refrigerant

• The cost of refrigerant has risen significantly in recent years, a result most likely driven by a combination of factors including a rise in the cost of raw materials, rising energy costs in producing the refrigerants, and the balance of supply and demand in a world where cooling is increasing in its use across an ever-rising population in both more established and developing economies.

It was reported by Öko-Recherche that in the first quarter of 2023, the increase in price in the EU for higher GWP refrigerants was large – R410a up 75%, R404a up 67%, and R134a up 48% in comparison to one year previously. Newer alternatives also saw increases, with R448a and R449a increasing 17% and 11% respectively.

The value of keeping refrigerant in the system continues to increase. While preventative maintenance should be the first action, all systems will leak to some degree and use of refrigerant gas detection equipment can identify this early enough to keep costs down through minimizing how much refrigerant is needed to top up the system.

Standards for Refrigerant Leak Detection

As in any industry, navigating the world of standards for refrigerant leak detection can be challenging. Typically, the standards documents run to hundreds of pages in length and finding the sections that apply to refrigerant gas detectors is only the first part of the challenge; understanding how to apply them comes next. Standards can be very localised to country or state, and often apply specifically to some cooling applications and not to others. There are, however, some standards that are more widely in force and can provide clarity on the basic requirements. These include standards in both Europe and the United States that clearly demand the installation of a refrigerant detection system.

The AIM Act

In the United States, the refrigeration sector is addressed directly by the American Innovation and Manufacturing Act. In the US EPA’s own words:

“Hydrofluorocarbons (HFCs) are potent greenhouse gases (GHGs). The American Innovation and Manufacturing (AIM) Act authorizes EPA to address HFCs by: phasing down their production and consumption, maximizing reclamation and minimizing releases from equipment, and facilitating the transition to next-generation technologies through sector-based restrictions on HFCs.”

Under subsection (h) of the AIM Act, “Management of Regulated Substances”, the EPA is authorised to promulgate certain regulations for the purposes of maximizing reclamation and minimizing releases of certain hydrofluorocarbons (HFCs) and substitutes from equipment. The over-arching goal of the program is to phase down HFC production and consumption by 85% from baseline levels by 2036. Many areas are covered within this, including regulations on leak repair, the use of reclaimed refrigerants in the installation or service of certain system types from January 2028, and the tracking of refrigerant containers and their use. One of the more immediate items covered is the requirement for installation of “Automatic Leak Detection (ALD) Systems” on refrigeration systems past a certain size threshold.

These rules apply to systems using a refrigerant with a GWP of 53 x CO₂ equivalence, a figure that is extremely hard to drop below when using HFCs.

The F-Gas Regulation

Similar in goal to the AIM Act, but with an additional decade of implementation behind it, in the European union the F-Gas Regulation is designed to reduce the use of HFCs and thereby the climate effect of their emission. The goal was set in the implementation of F-Gas in 2o14 to reduce HFC use by two-thirds by 2023 from baseline levels. Recently published in February 2024, the new F-Gas Regulation (EU) 2024/573 amends the previous Directive (EU) 2019/1937 and repeals the previous F-Gas Regulation (EU) 517/2014. The updated regulation has a yet more ambitious goal to reduce the amount of HFCs placed on the market by 98% by 2050 (compared to 2015).

Amidst the details of quotas, restrictions on use, monitoring, tracking, and enforcement, Article 6 the F-Gas Regulation clearly calls out the requirement for refrigerant leakage detection systems on refrigeration systems of a certain size, and specifies their minimum maintenance frequency.

Article 5 of the F-Gas Regulations calls out the requirement for systems to be manually checked for refrigerant leaks. The frequency for this requirement is halved if a refrigerant leak detection system is installed.

Reflecting on both the F-Gas Regulation and the AIM Act, once the requirement for installation of refrigerant gas detection has been identified, the next challenges are understanding the relevant refrigerant safety standards, then selecting the appropriate leak detection technology.

Refrigerant Safety Standards

Depending on the gas used, the dangers presented by leaking refrigerant can include asphyxiation, oxygen depletion, flammability, and toxicity. Measures to mitigate these risks are defined within refrigeration safety standards.

In Europe, the standard to follow is EN 378, Refrigerating Systems and Heat Pumps – Safety and Environmental Requirements. Of the four parts of EN 378, the one detailing the requirements around refrigerant gas detection is EN 378-3:2016+A1:2020, Installation Site and Personal Protection.

The principal standard governing refrigerant use in the USA is ASHRAE 15-2022. This standard aims to establish safeguards for life, limb, health, and property, prescribing safety requirements accordingly. Typically, it is necessary to reference ASHRAE 34-2022 alongside it, as this standard sets safety classifications for refrigerants and defines concentration limits for their safe use.

The objective of these standards is evident: to guarantee the safe handling of refrigerants and to safeguard the personnel operating in proximity to refrigeration systems. According to the ensuing stipulations of EN 378, the threshold for detecting leaks is determined by the Practical Limit. In comparison to the levels typically implemented on site, this is often notably high for refrigerants classified as A1 in terms of safety, often exceeding 15,000 ppm (parts per million) in many instances.

ASHRAE 15 takes a slightly different approach. The Refrigerant Concentration Limit (RCL) in the ASHRAE standard can be seen as similar to EN 378’s Practical Limit in that it looks at a gas concentration level where there is immediate danger to anyone exposed to it. Where the difference comes is that ASHRAE 15 stipulates that refrigerant gas detectors should alarm at a level no higher than the Occupational Exposure Limit (OEL) listed in ASHRAE 34; for A1 refrigerants, typically 1,000ppm.

It seems reasonable to draw a conclusion that a safe approach for A1 refrigerants is to set refrigerant gas alarms at 1,000ppm or lower. This is a level straightforward to achieve with a variety of refrigerant sensors and leak detection technologies.

A number of refrigerants are classified in other categories due to their flammability, toxicity, or a combination of those two factors. Examples include ammonia (NH₃/R717) classified as B2L, propane (R290) classified as A3, and the increasing number of refrigerants classified as A2L.

Refrigerant Safety Classification

For refrigerants outside of the A1 category, the refrigerant gas alarm levels are set to a concentration derived from either the toxic exposure limits, or the Lower Flammability Limit (LFL) of the gas – typically whichever is lower. This can create a need for different refrigerant leak detection technology and gas sensors to be used in order to effectively detect the refrigerant being used.

Refrigerant safety standards can also stipulate how refrigerant gas detectors should be implemented as part of a wider safety system. This can include integration with other risk mitigation operations, such as initiating a ventilation fan, shutting off power, or shutting down the refrigeration system.

The activation of audible and visual alarms is required in many applications. Although there are some differences per application or across different regions, audible and visual alarms typically required when a gas detection system is deployed in areas such as refrigeration machinery rooms, cold rooms, and occupied spaces. The differences come in ways including whether the alarms should be located inside the room, outside the room, or both, and whether there needs to be an alarm indication at a supervised location.

Some standards are very specific in the applications to which they apply, with a set of demands appropriate to the need beyond or outside of the more wide-ranging standards such as EN 378 and ASHRAE 15. These include IEC 60335-2-40, dealing with Particular requirements for electrical heat pumps, air-conditioners and dehumidifiers, and UL 60335-2-89, dealing with Particular Requirements for Commercial Refrigerating Appliances and Ice-Makers with an Incorporated or Remote Refrigerant Unit or Motor-Compressor. In these cases, with regard to refrigerant leak detectors to goal is to contribute to the overall safety of an appliance using flammable refrigerants, typically either A2L or A3. The demands for audio-visual alarms, for example, are not a part of the refrigerant gas detector’s job in these applications; rather they are there to initiate ventilation and stop machinery before there is a risk of explosion or flame from the leak of a flammable refrigerant.

Choosing the Right Refrigerant Gas Sensor

A wide variety of gas sensor technologies can be used to detect refrigerants. Each has its own particular set of advantages and disadvantages. The first point of consideration is what gas needs to be detected, and at what concentration level. Even within specific refrigerant sensor technology categories, there can be huge variation.

An example of this variation can be seen when reviewing infrared sensors for refrigerants. R32 is one of many refrigerant gases that can be detected via infrared absorption. Different sensors can detect at very different concentrations and come with very different prices, with an inverse relationship between the two factors. It is critical to understand what needs to be achieved by the sensor in order to select something that can do the job, but that doesn’t cost more than is needed to meet that requirement.

Example of R32 infrared sensor price vs. detection limit

In many instances, the same gas can be detected by different sensor types. R32 is another good example of this, being detectable by refrigerant sensor technologies including infrared, semiconductor, thermal conductivity, and more. In these cases, it is important to look at a cost-benefit analysis. Refrigerant gas detectors using semiconductor sensors can monitor at levels under 1,000ppm and are highly cost-effective – but they can suffer with cross-sensitivity to other gases and environmental factors to which infrared sensors are impervious but come with a higher price. Understanding how this balance effects a particular installation can be tricky, in which case expert guidance can be sought from specialists in refrigerant gas detection.

CO₂ is almost exclusively detected using infrared sensors in refrigerant applications, but not all sensors are the same. The measuring range can be different, the environmental specification can vary, and response times to a leak can be radically different. It is important not to equate indoor air quality sensors designed to react to gradually to changing atmospheric levels to a leak detector that needs to respond quickly to a rise in CO₂ levels in order to meet safety regulations and keep people safe from harm.

The response time of NH₃ sensors can also be critical, especially given the low concentrations at which NH₃ presents a danger through toxicity (typically <30ppm as a lowest level, local guidelines and regulations can vary). At low levels, electrochemical sensors are used for detection. The nature of this technology is that it depletes over time and sensors must be replaced, making regular service and maintenance of a NH₃ gas detection system especially important. Most sensors have a two- or three-year lifetime at best, though there are now options available with a lifetime of five years or more.

High Intention, Sincere Effort, and Intelligent Execution

Choosing which refrigerant gas detector to use, and implementing it into an effective gas detection system, is not always straightforward. But – if the intention is there to identify what needs to be achieved, and to put in the right system for that site, that application, and that user, the results can be excellent. It can take some effort to understand the various standards and regulations which need to be adhered to; it can be a complex decision which sensor technology to choose to effectively execute against that identified goal. This is where choosing the right partners is vital.

A refrigerant leak detection system needs not only to be purchased; it must also be installed and maintained. A good supplier who has a daily focus on refrigerant gas detection can help in navigating the world of gas detection standards and refrigerant sensor technology. After all, it is what they do all day every day, and they should understand it.

A reputable and experienced contractor can provide the installation services needed, with help and guidance from the supplier as appropriate, ensuring the gas detectors are installed in the right locations with the right connectivity to the rest of the refrigeration control and safety system. They can also ensure that the system is configured and commissioned correctly.

Maintenance should be planned for from day one. It is more than just a stipulation in the regulations – this service is essential to ensuring that the refrigerant leak detection system is functioning properly, accurately, and initiating all the mitigation needed in the event of a leak. Succinctly, it is there to do a job for the owner of the refrigeration system – protect people, protect the environment, and protect property.