Chlorofluorocarbons, better known as CFCs, were used primarily as refrigerants, aerosol propellants, foam-blowing agents, and industrial solvents. From the 1930s through the mid-1990s, they were among the most widely used industrial chemicals on the planet, found in everything from car air conditioners to hairspray cans to the insulation in building walls.
Why CFCs Were So Popular
Before CFCs existed, refrigerators relied on toxic gases like ammonia, methyl chloride, and sulfur dioxide to stay cold. These chemicals worked, but they were dangerous. A series of fatal accidents in the 1920s, caused by methyl chloride leaking from home refrigerators, pushed three major American companies (Frigidaire, General Motors, and Du Pont) to search for something safer.
In 1930, chemist Thomas Midgley Jr. was tasked with finding a refrigerant that was odorless, nontoxic, and nonflammable. Within three days, he identified dichlorodifluoromethane, which was soon sold commercially as Freon-12. The chemical checked every box. CFCs are nontoxic, nonflammable, and remarkably stable, meaning they don’t break down easily or react with other materials. That stability made them seem like a perfect fit for consumer products, and manufacturers adopted them rapidly across dozens of industries.
Refrigeration and Air Conditioning
The biggest use of CFCs was keeping things cold. CFC-12 (Freon-12) became the standard refrigerant in household refrigerators, commercial freezers, and vehicle air conditioning systems. It was used in car and truck AC units for over 30 years, from the early 1960s through the mid-1990s. CFC-11, a related compound, was the go-to refrigerant for large building chillers, the systems that cool office towers, hospitals, and shopping centers. Because of their safety record compared to ammonia and other older coolants, CFCs became the preferred option in virtually all cooling equipment worldwide.
Aerosol Propellants
If you used a spray can before the late 1970s, there was a good chance CFCs were doing the pushing. They served as the pressurized gas in aerosol cans for deodorants, hairsprays, insecticides, spray paints, and household cleaners. When you pressed the nozzle, CFCs carried the product out as a fine mist and then evaporated quickly without leaving residue or posing a fire risk. The United States banned CFCs in most aerosol products in 1978, making it one of the earliest regulatory actions against these chemicals, though many other countries continued using them in spray cans well into the 1980s.
Foam Manufacturing
CFCs played a critical role in making foam products. When injected into liquid plastic or rubber, they expanded into tiny bubbles that gave the material its lightweight, insulating structure. CFC-11 was widely used as a blowing agent for rigid polyurethane foam, the kind found in building insulation, refrigerator walls, and roofing panels. Softer foams used in furniture cushions, car seats, and packaging materials also relied on CFCs during manufacturing. Enormous quantities of CFCs remain trapped in old building insulation and appliances sitting in landfills today.
Industrial Solvents and Electronics Cleaning
CFCs were valuable as precision cleaning agents. CFC-113, in particular, was the industry standard for degreasing electronic circuit boards and removing flux residue after soldering. The semiconductor and aerospace industries relied on it because it dissolved oils and contaminants effectively, evaporated without leaving traces, and wouldn’t damage sensitive components. Metal parts manufacturers also used CFCs to degrease machinery components. Their chemical stability, the same trait that made them useful, turned out to be the core of the environmental problem.
How CFCs Damaged the Ozone Layer
The very stability that made CFCs safe at ground level meant they didn’t break down in the lower atmosphere. Instead, they drifted upward over years and decades until they reached the stratosphere. There, high above most of the ozone layer, the sun’s ultraviolet radiation finally broke them apart, releasing chlorine atoms. Those chlorine atoms set off a chain reaction: chlorine reacts with ozone, forming chlorine monoxide, which then reacts with more ozone molecules. A single chlorine atom can destroy thousands of ozone molecules before it’s neutralized. This process carved a massive hole in the ozone layer over Antarctica, thinning the shield that protects life on Earth from harmful UV radiation.
The Global Ban
The Montreal Protocol, signed in 1987, established a timeline for phasing out CFC production worldwide. CFCs were classified as the most damaging category of ozone-depleting substances and have been completely phased out of production, with only very limited exemptions. The ban is widely considered one of the most successful international environmental agreements ever negotiated, with universal participation from countries around the world.
Recovery, however, is slow. The banned chemicals persist in old products like building insulation and in landfills, continuing to leak into the atmosphere. NASA and NOAA have confirmed that the ozone hole is trending smaller than it was in the early 2000s, forming later in the season and breaking up earlier. The 2025 Antarctic ozone hole ranked as the fifth smallest since 1992. But projections show the ozone layer won’t fully recover to 1980s levels until around the late 2060s.
What Replaced CFCs
The transition away from CFCs happened in stages. The first generation of replacements, called HCFCs, still contained chlorine but broke down faster in the atmosphere, causing less ozone damage. Those are now being phased out as well. The next wave, HFCs, eliminated the ozone problem entirely but turned out to be potent greenhouse gases, trapping thousands of times more heat than carbon dioxide.
Today’s replacements are designed to address both problems. In car air conditioning, a newer refrigerant called HFO-1234yf has become the global standard, replacing the HFC that originally replaced CFC-12. Similar compounds are now used in foam blowing, commercial refrigeration, aerosol products, and industrial cleaning. These newer chemicals break down in the atmosphere within days or weeks rather than persisting for decades, giving them a fraction of the climate impact of the chemicals they replaced.