Preventing ozone depletion comes down to eliminating the chemicals that destroy ozone molecules in the stratosphere and keeping the ones still in circulation from escaping into the atmosphere. The global effort that started with the 1987 Montreal Protocol has already proven this works: NASA projects the ozone layer could fully recover by 2066. But that timeline depends on continued action at every level, from international agreements to how you dispose of an old refrigerator.
The Chemicals That Destroy the Ozone Layer
Ozone-depleting substances (ODS) include chlorofluorocarbons (CFCs), halons, carbon tetrachloride, methyl bromide, and hydrochlorofluorocarbons (HCFCs). These compounds were once widely used in refrigeration, air conditioning, aerosol sprays, foam insulation, fire extinguishers, and agricultural fumigation. When released, they drift into the stratosphere where ultraviolet radiation breaks them apart, freeing chlorine or bromine atoms that catalytically destroy ozone molecules. A single chlorine atom can destroy thousands of ozone molecules before it’s neutralized.
CFCs are the most well-known offenders. CFC-12, once the standard refrigerant in cars and home appliances, persists in the atmosphere for about 100 years. Halons, used in fire suppression systems, are even more destructive per molecule. Halon 1301 has an ozone-depleting potential roughly 16 times that of CFC-11, the benchmark compound.
The newest major threat is one most people don’t associate with ozone at all: nitrous oxide. Since the Montreal Protocol successfully cut halocarbon emissions, nitrous oxide has become the single largest ozone-destroying compound emitted by human activities, measured by its ozone-depleting potential. About 10 percent of the nitrous oxide that reaches the stratosphere converts into nitrogen oxides, which break down ozone through a separate chemical cycle. The primary sources are agricultural soils (driven by nitrogen fertilizer use), livestock waste, and industrial processes.
How International Agreements Phase Out ODS
The Montreal Protocol, signed in 1987, is the backbone of ozone protection. It set binding schedules to phase out production and consumption of CFCs, halons, carbon tetrachloride, and methyl bromide. It’s widely considered the most successful environmental treaty ever enacted, with 198 parties ratifying it.
The 2016 Kigali Amendment extended this framework to hydrofluorocarbons (HFCs). HFCs were introduced as replacements for CFCs and don’t directly harm the ozone layer, but they’re potent greenhouse gases that indirectly affect atmospheric chemistry. The Kigali Amendment targets an 85 percent phase-down in developed countries by 2036. Most developing countries, including China, will freeze HFC consumption in 2024, begin reductions in 2029, and complete an 80 percent phase-down by 2045. A smaller group that includes India will freeze consumption in 2028 and reach an 85 percent reduction by 2047.
In the United States, the Clean Air Act’s Title VI enforces these commitments domestically. Production and import of virgin halons ended on January 1, 1994. Methyl bromide production for most uses was phased out on January 1, 2005, though limited exemptions remain for quarantine treatments (like fumigating imported logs to stop wood-boring pests) and situations where no viable alternative exists.
What You Can Do at Home
The most impactful thing individuals can do is ensure that refrigerants in their appliances and vehicles never vent into the atmosphere. Every older refrigerator, window AC unit, and car air conditioning system contains refrigerant that, if released, contributes to ozone depletion or climate change or both.
Dispose of Appliances Properly
When getting rid of an old refrigerator, freezer, or air conditioner, don’t just leave it on the curb. Start by checking whether your electric utility offers a rebate or appliance turn-in program. Many utilities will pick up old refrigerators for free and pay you a small bounty because decommissioning inefficient units saves energy across the grid. Your local municipality may also accept refrigerated appliances, though some require a certified technician to recover the refrigerant before pickup. If neither option is available, contact a local retailer or recycling organization. Proper appliance recycling involves recovering the refrigerant, removing hazardous components, and then shredding the evacuated unit.
Maintain Your Car’s AC System
Small refrigerant leaks in vehicle air conditioning systems are common and add up across millions of cars. If your car’s AC isn’t cooling as well as it used to, that’s often a sign refrigerant is escaping. Have the system inspected rather than simply topping it off, since recharging a leaking system just puts more refrigerant on a path to the atmosphere. A mechanic can pressure-test the system, find the leak, and repair it. For minor leaks, stop-leak products applied through the low-pressure service port can temporarily seal small gaps, but persistent cooling problems or unusual noises from the compressor call for a proper mechanical repair.
Choose Better Cooling Equipment
When replacing an air conditioner or heat pump, look for systems that use lower-impact refrigerants. The most common residential refrigerant today, R-410A, has a global warming potential of 2,088, meaning one kilogram released traps as much heat as over two metric tons of carbon dioxide. Newer alternatives are entering the market with significantly lower numbers. R-466A, for example, has a GWP of 733 (65 percent lower than R-410A) and is non-flammable, making it a practical drop-in option. R-452B offers about a 5 percent efficiency improvement in hot conditions. Natural refrigerants like propane (R-290) have a GWP under 5 and are already used in some commercial refrigeration systems in Europe, though flammability limits their residential applications in some markets.
Fire Suppression and Industrial Sources
Halons remain in use in certain fire suppression systems, particularly on commercial aircraft, in legacy military equipment, and in oil and gas operations. Since no new halons can be manufactured or imported in the United States, the existing supply comes entirely from recycled stocks. The EPA prohibits venting halons during testing, maintenance, or disposal of halon-containing equipment. If you manage a building or facility that still uses a halon fire suppression system, sending the equipment to a certified recovery facility when decommissioning is a legal requirement, not just a best practice. Suitable alternatives exist for most applications.
Carbon tetrachloride and methyl chloroform, once common industrial solvents, have been largely phased out, but some developing countries still use them in limited quantities. Supporting and complying with the Montreal Protocol’s trade restrictions keeps these chemicals from re-entering supply chains.
Tackling Nitrous Oxide Emissions
Because nitrous oxide is now the dominant ozone-depleting emission from human activity, addressing it is essential for long-term ozone recovery. Unlike CFCs and halons, nitrous oxide isn’t covered by the Montreal Protocol. The largest anthropogenic source is soil microbial activity amplified by synthetic nitrogen fertilizers. Reducing over-application of fertilizer, using slow-release formulations, and adopting precision agriculture techniques that match nitrogen inputs to crop needs all cut emissions. Livestock manure management, wastewater treatment, and certain industrial processes (particularly nitric acid production) are smaller but meaningful sources where proven reduction technologies exist.
Reductions in nitrous oxide emissions now represent a larger opportunity for reducing future ozone depletion than controlling any remaining unregulated halocarbon. This makes agricultural and industrial nitrous oxide policy the next frontier of ozone protection, even though it’s rarely framed that way in public discussion.
Why the Recovery Timeline Still Matters
The ozone layer is healing, but the projected 2066 recovery date assumes full global compliance with existing agreements. Any backsliding, whether through illegal CFC production (which has been detected in past years), slow adoption of HFC alternatives, or rising nitrous oxide emissions, pushes that date further out. The Antarctic ozone hole still forms every spring, and Arctic ozone depletion events have intensified in some recent years due to unusually cold stratospheric temperatures linked to climate change.
The connection between ozone depletion and climate change runs both ways. Many ozone-depleting substances are also powerful greenhouse gases. CFC-12 traps over 10,000 times more heat per molecule than carbon dioxide. By eliminating these chemicals, the Montreal Protocol has prevented an estimated amount of warming that rivals the effect of the Kyoto Protocol’s carbon targets. Choosing low-GWP refrigerants, maintaining sealed cooling systems, and supporting agricultural reforms that cut nitrous oxide all serve both goals simultaneously.