From the Montreal Protocol to the Paris Agreement: How Refrigerants Have Felt the Chill of Global Environmental Regulations


International refrigerant related environmental regulation began in a laboratory at the University of California, Irvine, in 1973 when a postdoctoral fellow, Mario J. Molina, under the supervision of F. Sherwood Rowland, made a groundbreaking and controversial hypothesis that chlorofluorocarbons (CFCs) could destroy ozone (O3) in the Earth’s stratosphere.

CFCs, synthetic chemicals classified as halocarbons, are composed of carbon, fluorine, and chlorine. CFCs can also be manufactured to contain hydrogen in place of one or more chlorines; these are called hydrochlorofluorocarbons (HCFCs). These stable molecules degrade very slowly once released to the atmosphere and can hang around for hundreds of years in the lower atmosphere before making their way to the outer layer of the atmosphere called the stratosphere.

At the time of Molina’s discovery, CFCs were used plentifully in applications that enhanced quality of life for many people: refrigeration, airconditioning, and aerosol spray cans all employed the compound in some fashion. CFCs were well suited to these applications as they are considered nontoxic and nonflammable, and they are readily converted from a liquid to a gas and vice versa. These stable compounds can also be used quite safely in close proximity to humans with little to no threat to life or health upon contact.

Molina’s hypothesis that CFCs could destroy ozone was based on a theory that photons from ultraviolet light could break CFCs apart to release chlorine atoms and other products. Because the chlorine atom has an unpaired electron it is considered a radical, meaning that it can easily react with ozone molecules breaking them apart. CFCs slowly make their way to the stratosphere where they are bombarded by high-intensity ultraviolet light which in turn splits the molecule into its building block components. Chlorine is then free to attack ozone molecules at will. Later studies found that 1 chlorine atom has the potential to break down 100,000 ozone molecules alone.

Molina’s discovery was so significant because ozone comprises the stratospheric ozone layer, which surrounds the earth like a delicate protective atmospheric eggshell. Discovered in 1913 by a team of French scientists, the ozone layer protects us from the harmful effects of the sun by absorbing and filtering ultraviolet rays. UV rays in high concentrations or intensity cause several adverse health effects, including skin cancer, cataracts, and impaired immune systems. They have also been found to damage delicate food crops like soybeans along with animal and marine life. Put simply, a little sun is good, a lot of sun is bad, and the ozone layer protects us from a lot of sun.

In 1985, a team of English scientists validated Molina’s hypothesis through the discovery of a rapidly growing stratospheric ozone hole at the South Pole. Once considered natural thinning and reforming, they found that the ozone was no longer reforming to its prior state after each spring thaw. Instead, it began to thin and continued to thin. In scientific fact, a giant hole was forming in the ozone layer that could no longer naturally repair itself, and CFCs were directly to blame.


What did all this mean for refrigeration? As noted previously, at the time of Molina’s discovery, CFCs were in wide use as coolants in refrigeration and airconditioning systems worldwide. That CFCs were inert and non-toxic made them well suited as refrigerants, particularly for use in units that most people use in their homes every day.

The concept of refrigeration is not new to humankind; it has been around for thousands of years. From the use of naturally formed ice blocks harvested from rivers and lakes to the invention of mechanical refrigeration in the mid-1800s, refrigeration is a staple convenience for most people. Refrigeration stops the progress of bacteria on foodstuff, helping food stay fresh longer. According to the U.S. Department of Agriculture, the refrigerator is one of the most important pieces of kitchen equipment for keeping food safe. From the field to the table, refrigeration – whether in industrial (cold storage and distribution warehouses), commercial (local grocery stores), or residential (home appliances) – touches everyone’s life by keeping food fresh, safe, and readily available for consumption. It has implications in other industries including longevity of pharmaceuticals and lifesaving drugs as well.

When mechanical refrigeration was invented, the first refrigerants used, like anhydrous ammonia (NH3), methyl chloride (CH3Cl), and sulfur dioxide (SO2) were easily synthesized and quite readily manipulated from gas to liquid, a necessary attribute for the mechanical refrigeration process. They were also naturally occurring compounds, meaning they occur naturally in the environment. Unlike CFCs, Mother Nature makes them, and Mother Nature disposes of them with little to no adverse effect on the environment. However, these refrigerants have properties that make them both potentially toxic and flammable and consequently can be dangerous to human health.

In 1928, Thomas Midgely, an American inventor, developed CFCs as an alternative to those refrigerants first used when mechanical refrigeration was invented, addressing the issues of toxicity and flammability of these early, albeit environmentally friendly refrigerants. CFCs along with HCFCs, were manufactured with good intentions in order to solve a problem regarding industrialization and to mitigate risk to human health.

As soon as DuPont mass produced the first CFC compound in the 1930s, refrigeration units in every home became a possibility, and as technology and raw materials were prioritized for use in home appliances, refrigeration units in every home soon became a reality. Because CFCs were deemed physically safe, they weren’t heavily regulated at the time. Dumping CFCs into the atmosphere, through leaky or poorly maintained refrigeration systems was considered inconsequential. You were really just out the cost of replacing the refrigerant, which at the time, was relatively inexpensive. No one yet knew what was happening to CFCs high up in the atmosphere. Save for their one fatal flaw, they were ideal refrigerants – stable, energy efficient, safe to use around people, and ultimately beneficial to improving quality of life.


After discovery of the widening ozone hole in the Antarctic in 1985, which the research of Molina had predicted in 1973, CFCs were now considered public enemy number one on a global scale. The man-made substance that was meant to help humans thrive was now found to be detrimental to their health along with the health of all life on Earth.

The global community took notice and then acted. CFCs were not only a point source pollutant, meaning their release and subsequent breakdown only affected local or immediately adjacent areas, they also affected the entire world by travelling to the highest reaches of our atmosphere and damaging the protective stratospheric ozone layer. CFCs were a global pollutant. Everyone everywhere would be made particularly vulnerable to the effects of increased solar radiation, and something had to be done about it.

In 1987, as a result of the 1985 United Nations (UN) Vienna Convention for the Protection of the Ozone Layer, the Montreal Protocol on Substances that Deplete the Ozone Layer was signed into force and ratified by every nation in the world. No other treaty before or since has had the same signing power of the Montreal Protocol. Every nation on Earth came together to help mitigate and prevent the effects of CFCs and subsequently HCFCs on the stratospheric ozone layer. According to the UN this treaty is the most successful global environmental action to date.

Initially, parties to the Montreal Protocol agreed to cut CFCs by 50 percent over 12 years, but, due to initial success, they swiftly accelerated the reduction rate to 100 per-cent by 1992. In its 30-year history, the treaty has resulted in the reduction of nearly 100 ozonedepleting (ODP) chemicals by nearly 100 percent. Manufacturing or producing CFCs is now illegal and has been banned since 1996. Manufacturing and producing HCFCs will be illegal in the next 10 years as well.

The good news is that the due to the Montreal Protocol and subsequent commitment to phase-out ODP substances, the ozone layer is beginning to heal and, according to the UN, is likely to recover completely in the next several decades.

The universal success of the Montreal Protocol is due to several factors. First, stratospheric ozone depletion was the first truly global environmental challenge that the world had been exposed to collectively. The concern it caused unified independent nation states and made it easy for them to come together to address the issue in a real way. Second, national governments, like the Unites States, had already made strides to phase-out CFCs prior to the formation of the treaty. The U.S. Environmental Protection Agency (EPA), for instance, went to great lengths to regulate these compounds as part of the Toxic Substances Control Act in the late 1970’s based on Molina’s research alone. Third, the general public learned of the controversy and started pushing back on industry by boycotting the use of CFCs in consumer products, essentially refusing to participate in purchasing products that contained the substances. Finally, and maybe most importantly, private industry, having received clear signals from scientists, government, and the general public, were already moving in the direction of replacing CFCs and HCFCs with new alternatives.


Indeed, seeing profits diminish, facing unwieldy regulation, and learning of potential environmental damage, industry had already begun working on creating and developing CFC alternatives long before the Montreal Protocol was signed into force. When the Montreal Protocol was brought to the table, hydrofluorocarbons (HFCs), compounds comprised of hydrogen, fluorine, and carbon, were already in production and nearly ready for market. Many of these HFCs were also acceptable drop-ins for CFC and HCFC refrigerants already in use, which made the transition even easier. In fact, DuPont, a market leader in CFC production, was an enthusiastic champion of the Montreal Protocol mainly because the company was already poised to bring new alternatives to the marketplace. The public, government, industry, and the world were prepared for the change. Together they made it happen, and it happened rapidly. HFCs quickly became the immediate answer to the nasty ODP substances of the past. They were engineered to eliminate chlorine and in so doing become a zero ODP substance. Fitting nicely into the mandates of the Montreal Protocol, HFCs could be, with a small amount of retrofitting, used in much the same way and in the same applications as CFCs and HCFCs with many of the same beneficial effects. In the meantime, while HFCs were being phased-in as substitutes for CFCs and HCFCs, the international scientific community was hard at work outlining a new global environmental problem better known as global warming. Scientific study of the subject of global warming and climate change ramped up precipitously in the mid 1990’s buoyed by the success of the Montreal Protocol and the discoveries made regarding the atmosphere therein. HFCS AND GLOBAL WARMING Global warming is the idea that the overall temperature of the Earth is gradually increasing. This gradual increase in temperature is attributed to the greenhouse gas effect, which is caused by increased levels of carbon dioxide, methane, nitrous oxide, HFCs, and other pollutants known as greenhouse gases (GHGs). GHGs are substances that trap the sun’s radiation in the Earth’s atmosphere, making the Earth warmer. Fluorine, a primary building block of HFCs, was found to be one of the most highly potent GHGs of them all, thousands of times more potent than carbon dioxide. HFCs are considered to have a very high global warming potential (GWP).

An elegant solution to one global environmental problem had quickly become a primary offender of another.


The first international attempt at regulating HFCs as part of a larger, comprehensive GHG emission phasedown directive began in 1992 with the formation of the United Nations Framework Convention on Climate Change (UNFCCC) convened in Rio de Janeiro, Brazil as part of the UN Earth Summit program. During this first meeting it was agreed by member states that climate change in the form of global warming was in fact occurring and that human activity had a forcing effect on this change. The goals outlined in this convention were meant to prevent irreparable harm to the climate due to man-made activities. Over 190 countries, including the United States, agreed to participate and continue to meet annually to discuss the effects of climate change worldwide. These meetings have resulted in two key legally binding international treaties affecting GHGs, the 1997 Kyoto Protocol and the 2016 Paris Agreement.


The Kyoto Protocol was adopted on December 11, 1997 with the intent to set internationally binding GHG emission reduction targets in order to combat the man-made effect on climate change. This treaty focused on obtaining support of industrialized nations to agree to voluntarily phase-down their total amount of GHG emissions. Developing countries were exempted but asked to participate voluntarily. The treaty has faced a lack of consensus primarily due to the fact that only industrialized nations were to be made legally responsible for emission phase-down targets. There has also been some controversy with regard to clean development and emissions trading programs as part of the treaty. Both the United States and Canada have pulled out of this agreement, however, many countries like Australia and the European Union (EU), which is currently comprised of 28 European member countries, have only just recently committed to new binding phase-down targets. Many HFC regulations, particularly in the EU, have been born from participation in this treaty.


On December 12, 2015, parties to the UNCCC reached a landmark agreement to combat climate change and intensify the actions and investments needed to curb GHG emissions. Considering lessons learned from the Kyoto Protocol, this treaty focused not only on phasedown of emissions, but also with mitigation, adaptation and financing programs to help create a sustainable future. The Paris Agreement brought both industrialized and developing nations together to undertake ambitious efforts to combat climate change.

The Paris Agreement is a more overarching treaty on global warming and climate change and is based on voluntary nationally determined contributions (NDCs). It also includes a method to provide monetary support to assist developing countries to participate. While not receiving universal adoption, the Paris Agreement has been signed into force by over 80 percent of the parties to the UNCCC at this time. While, many of it’s primary trading partners have signed the treaty, including Canada, Mexico and the United Kingdom (U.K.), the United States has currently withdrawn from this agreement.


Based on all the new data regarding climate change and global warming, the Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer was negotiated in 2016. It has since been ratified by 79 nations at the time of this writing. Directly targeting HFCs as GWP substances, all nations participating have agreed to gradually phase-down HFCs by more than 80 percent over the next 30 years and replace them with more environmentally friendly alternatives.

Immediately surprising to the international community was that nations that had originally participated in the Montreal Protocol did not readily sign on to the Kigali Amendment. The United States was one of those nations. Less than half of the UN member nations have currently ratified this treaty. It was clear that the Kigali Amendment lacked the enthusiasm and the popular support of the Montreal Protocol and we are left to ask ourselves why.

Climate change and global warming are subjects that are confusing to many people. Endless media bombardment of polarized global warming and climate change opinions has made the public skeptical of what they see and hear on the news and from the scientific community. When the issue of the stratospheric ozone layer was introduced, little time was wasted between identification of the problem and implementation of the solution, leaving no time at all for confusing alternate theories to be suggested or supported.

The concept of climate change or global warming is also less tangible and more complicated than the concept of the stratospheric ozone layer. Climate change affects many Earth Systems in a multitude of ways, with both human interference and natural Earth cycles contributing to the problem. It does not hang on one major substance either; many high GWP pollutants and industries contribute to the problem of global warming. It’s not as easy as declaring that phasing out HFCs will immediately fix or, in fact, have any significant effect on the problem at all.

Finally, and again likely the most important reason, industry is not already sitting on powerful new acceptable alternatives ready to be brought to market. Markets are simply not poised to make an easy transition. HFCs fit nicely as substitutes for CFCs and HCFCs, but similar obvious or easy substitutes are not available for HFCs.

United States and HFC Regulation Even though the United States has decidedly pulled back from participation in international treaties involving HFC and total GHG emissions phase-down programs, there is still HFC regulation being pushed through at the state and federal level.

When the United States unexpectedly pulled out of the Paris Agreement, many U.S. states were emboldened to create their own alliance in 2018. The U.S. Climate Alliance, at the time of this writing, includes 25 U.S. states wherein each member state has agreed to implement policies that advance the goals of the Paris Agreement, aiming to reduce greenhouse gas emissions by at least 26- 28 percent below 2005 levels by 2025. HFCs are considered low-hanging fruit regarding GHG emissions and will likely be phased down at the state level within the scope of the alliance’s objectives.

The EPA has also attempted to regulate HFCs at the federal level. Having overseen the transition away from ODP substances per regulation created through participation in the Montreal Protocol, the EPA attempted to regulate HFCs and substances with high GWP in much the same manner as ODP substances.

The EPA’s Significant New Alternatives Policy (SNAP) program was established under the Clean Air Act to identify and evaluate acceptable substitutes for ODP substances. Its primary purpose was to help industry transition to new acceptable non-ODP substances. At the time the program was created, HFCs were considered acceptable substitutes, however, all that changed in 2015 when the EPA expanded the scope of the SNAP program to include acceptable new alternatives to GWP substances, meaning that HFCs were now on the chopping block if an acceptable new alternative was readily available for use to replace them.

The EPA was summarily sued by an HFC manufacturer and the legal finding, held up by the D.C Circuit Court of Appeals, was mostly in favor of the manufacturer. It essentially found that the EPA had exceeded its authority by using a program meant to eliminate ODP substances in order to regulate HFCs as high GWP substances. Environmental groups, however, are currently poised to sue the EPA in an effort to resurrect the program mandate on GWP substances once again. In short, increased U.S. regulation through federal mandate with respect to HFCs is not completely out of the question just yet.

It is also important to note that the Kigali Amendment remains in play here in the United States as well. It is still sitting on the President’s desk waiting for a signature and is considered not off the table just yet. Many industry stakeholders remain keen for the President to support the Kigali Amendment, citing an increase in economic opportunity and job development if the amendment were to be ratified. Again, it remains to be seen how this will play out.

The United States is also facing a lot of International pressure to sign on to the Paris Agreement, with arguments that China and India are more likely to comply with GHG phase-down objectives if we do.

On the international stage, many of the United States’ primary trading partners have signed all three treaties; the Kyoto Protocol, Paris Agreement and the Kigali Amendment. The EU, for instance, is a primary driver in phasing down HFC refrigerants on the world stage with strict F-gas regulations already in force. Canada is also not far behind.


It is easy to conclude that based on the international movement toward the phase-down of GWP substances, that HFCs have a very uncertain future. Evolving regulation and competing industry investments do not guarantee that they are a safe bet to employ as the refrigerant of choice moving forward. But what are the potential alternatives? Lower GWP HFCs, hydrofluoro-olefin (HFO), and HFO-HFC blends have all been proposed as possible alternatives to current high GWP HFC refrigerants.

Lower GWP often comes with one drawback though, increase in potential flammability. None of these options has yet become the leader of the pack.

HFO refrigerants have lower GWP because they are highly unstable compounds, this same instability is a leading factor in an HFO’s propensity to break down under high temperatures. Certain HFOs can be quite flammable as well. When these HFOs are burned they create hydrogen fluoride, add a little water to the equation and you get hydrofluoric acid which can contaminate water supplies. Hydrofluoric acid has been known to dissolve glass. Hydrogen fluoride can also cause deep chemical burns, absorbing through the skin where it can have long-lasting effects on human health far beyond initial contact.

HFOs are often blended with HFCs, however, this blend is essentially just upping the GWP of the HFO and increasing the flammability and potential toxicity of the HFC. HFC and natural refrigerant blends have also been suggested. The drawback with any blend is that most have a habit of separating, and thus, producing what is termed “glide’ – when a refrigerant blend begins to separate over time, the performance characteristic begins to change or glide – which makes them a less than ideal substitute in practical application.

One thing is for sure though, the market is heavily investing in the research and development of new alternatives to HFCs, hoping to manufacture the perfect compound that is both good for the environment without forcing global warming and good for people without causing immediate harm to health.


NH3 has been widely and consistently used in industrial refrigeration applications since the 1800s. It can be argued that it is the longest-lived refrigerant still on the market. NH3 has excellent thermodynamic properties and high energy efficiencies when used in refrigeration systems which made it hard to move away from on an industrial scale. And, the long and successful use of NH3 in industrial systems proves that its hazards are easily managed. New technology in refrigeration equipment has also made it possible to lower NH3 loads, meaning less of the refrigerant is needed to create a similar effect. This essentially makes the use of NH3 around people and in new applications much safer. Safety standards and codes have also been developed specifically for the NH3 community making the industry safer throughout the years. Toxicity and flammability issues with better technology, lower charges, and increased safety measures make NH3 a good refrigerant to count on. NH3 is a time-tested refrigerant that has proven that it can be made safe to use, is energy efficient, and good for the environment.

CO2 is another natural refrigerant that has made great strides in practical application in recent years. The benefit of CO2 is that it is neither toxic nor flammable and can be used in close proximity to people with a low immediate threat to health. It has found a niche in food retail as many grocery stores have voluntarily decided to move away from the use of HFCs via corporate mandated environmental sustainability programs. The only issue with CO2 is that it can be difficult to manage as it requires higher system pressures and there are limitations to its geographical application due to ambient temperature and humidity issues. However, those issues are being addressed with new advances in technology as well.

Other natural refrigerants including hydrocarbons (propane), water, and air are all still being considered as possible alternate replacements to HFCs through the adaptation of new technology and safer system designs.

Refrigeration increases food safety, prevents food loss and helps feed the masses of the world. For those reasons alone it is here to stay. With population projected to explode in the next 30 years, with some estimates reaching the 11 billion mark, the need for refrigeration becomes more imperative. However, ever increasing regulation and concern for the environment has put the refrigeration market on the defense and looking for a sustainable future.

Without a clear path forward where do we go? We go back to the beginning with natural refrigerants and better technology. NH3, CO2 , propane and other naturals have the potential to become the last refrigerants that ever need be applied to modern refrigeration applications. With regard to regulation of refrigerants, the way back becomes our way forward.


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