The term “Freon” is a registered trademark used as a generic name for a group of fluorocarbon refrigerants used in air conditioning and refrigeration systems. These chemicals were initially celebrated for being stable, nonflammable, and nontoxic, replacing hazardous predecessors like ammonia. However, scientific discoveries revealed that these compounds posed a significant threat to the global environment, leading to a worldwide regulatory effort to phase them out. The international community has since moved through two distinct phases of regulation, first targeting chemicals that destroy the ozone layer and then focusing on those that contribute to climate change.
Ozone Depletion and the First Regulatory Wave
The primary scientific driver for the first phase-out was the discovery that certain refrigerants possessed a high Ozone Depletion Potential (ODP). The stratospheric ozone layer acts as Earth’s natural shield, protecting life from the sun’s harmful ultraviolet (UV) radiation. In the 1970s and 1980s, scientists confirmed that man-made compounds were damaging this protective layer, leading to the formation of the “ozone hole” over Antarctica.
The chlorine and bromine atoms within these compounds travel to the stratosphere and catalyze the destruction of ozone molecules. This scientific consensus led to the creation of the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987, a landmark international treaty. The protocol established a mandatory, step-wise timetable for countries to cease the production and consumption of chemicals with high ODP.
Identifying the Specific Phased-Out Chemicals
The first category of refrigerants targeted and completely phased out under the Montreal Protocol was Chlorofluorocarbons (CFCs). CFCs, such as R-12, were once widely used in car air conditioning, refrigerators, and aerosol propellants. These chemicals contained a high concentration of chlorine, giving them a very high ODP, and their production and import in developed nations were banned in the mid-1990s.
The second group to be phased out was Hydrochlorofluorocarbons (HCFCs), which were introduced as transitional substitutes because they had a lower ODP than CFCs. The most notable HCFC being phased out is R-22. While R-22 was less damaging to the ozone layer than R-12, it still contained chlorine and thus had a measurable ODP. The production and import of R-22 in the United States and other developed nations completely ceased in January 2020, with the final phase-out of all HCFCs scheduled for 2030. After the production ban, the servicing of existing equipment running on R-22 relies only on recycled or previously stockpiled quantities.
The Shift to Global Warming Potential
The chemicals that replaced CFCs and HCFCs were primarily Hydrofluorocarbons (HFCs), such as R-410A. HFCs were initially considered acceptable because they contain no chlorine, giving them an Ozone Depletion Potential of zero. However, HFCs posed a serious environmental threat due to their high Global Warming Potential (GWP).
GWP is a metric that quantifies how much heat a gas traps in the atmosphere compared to the same mass of carbon dioxide. HFCs are potent greenhouse gases, often hundreds or thousands of times more effective at trapping heat than carbon dioxide. For instance, R-410A has a GWP over 2,000, meaning one pound of R-410A released has the same warming effect as 2,000 pounds of carbon dioxide. This environmental concern spurred the 2016 Kigali Amendment to the Montreal Protocol, which aims to phase down the production and consumption of HFCs globally by 80–85% by 2047. In the United States, the American Innovation and Manufacturing (AIM) Act of 2020 implements this phasedown domestically.
Modern Refrigerant Replacements
The current regulatory landscape is driving the industry toward third-generation refrigerants characterized by ultra-low GWP. These modern alternatives fall mainly into two groups: Hydrofluoroolefins (HFOs) and natural refrigerants. HFOs, like R-1234yf, are synthetic compounds that have zero ODP and a very low GWP, typically less than 10. They break down much more quickly in the atmosphere than HFCs, significantly reducing their climate impact.
Natural refrigerants are substances that occur in nature, including propane, carbon dioxide, and ammonia. Propane has excellent energy efficiency but is flammable, requiring specific safety standards for its use. Carbon dioxide has a GWP of just 1, but it operates at very high pressures, necessitating robust system designs. The transition to these low-GWP refrigerants requires the replacement of existing equipment, as the new alternatives often have different operating characteristics and safety classifications.