Interactively compute the ODP, GWP, atmospheric lifetime, CFC-11 equivalent and CO2 equivalent emissions, and the projected recovery year for CFCs, HCFCs, HFCs and halons. See how the Montreal Protocol global controls reshape stratospheric chemistry decade by decade.
Parameters
Compound (ODS / replacement)
Sets ODP, GWP and atmospheric lifetime
Annual emission
ton/yr
Yearly atmospheric release (tons)
Atmospheric lifetime
year
Average years before tropospheric breakdown
Baseline concentration
ppt
Current tropospheric mixing ratio (pptv)
Cl atoms / molecule
Number of chlorine atoms per molecule (CFC-11 = 3)
Br atoms / molecule
Number of bromine atoms per molecule (large for halons)
Results
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ODP (CFC-11 = 1.0)
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GWP (100yr CO₂ eq)
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Lifetime (year)
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CFC-11 eq emission (ton)
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CO₂ eq emission (Mton/yr)
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Recovery year
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Stratospheric ozone destruction chain
After UV photolysis in the stratosphere, ODS molecules release Cl and Br radicals that catalytically destroy ozone. One Cl atom can destroy roughly 100,000 O₃ molecules.
First-order estimate of the recovery year. baseYear = 1986 (peak ODS emission); τ_atm is the atmospheric lifetime [year]. Actual recovery depends on Protocol compliance and other species.
Ozone Depletion and ODS (Ozone-Depleting Substances) — The Montreal Protocol
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I remember hearing about the "hole in the ozone layer over Antarctica" years ago, and that spray cans were to blame. Is that still a thing today?
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Good memory. In 1985 the British Antarctic Survey discovered that springtime Antarctic ozone was dropping by 60%. The culprits were the CFCs (chlorofluorocarbons, "Freons") that the world was producing in huge quantities as refrigerants, foam blowing agents and spray propellants. CFCs are basically inert at ground level — and that's the problem: they don't break down in the troposphere, so they slowly drift up to the stratosphere (20-30 km), where UV photolysis releases chlorine radicals Cl·. Those Cl atoms then destroy ozone catalytically.
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What does "catalytically" mean here? Doesn't the Cl just hit one O₃ and stop?
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That's exactly what makes ozone depletion so dangerous. The cycle is Cl + O₃ → ClO + O₂, then ClO + O → Cl + O₂. The Cl atom is regenerated, so one atom keeps destroying ozone over and over. Measurements suggest a single Cl atom can destroy on the order of 100,000 ozone molecules before it is finally removed from the stratosphere. So even at ppt (parts per trillion) abundances, the impact is enormous. Pick "CFC-11" on the left and you see ODP = 1.0 with a 45-year lifetime — that's a catalyst running upstairs for half a century.
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Cranking up the Br slider makes EESC jump dramatically. What is a halon exactly?
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Halons are brominated halocarbons that used to be common fire suppressants — Halon-1301 (CBrF₃) is the textbook example. Br runs the same catalytic cycle as Cl, but about 60 times more efficiently because of additional pathways like BrO + BrO and ClO-BrO coupling. That is why the EESC formula multiplies Br by ~60. Switch the compound to Halon-1301 with Br = 1 and you'll see ODP shoot to 16 — meaning gram-for-gram it destroys 16× more ozone than CFC-11.
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If I pick HFC-134a, the ODP becomes 0 and the verdict turns "OK". So the problem is solved, right?
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That's the modern twist. HFCs contain no chlorine or bromine, so they don't damage ozone (ODP = 0). But look at the GWP: HFC-134a is 1,430 — that's 1,430× the warming impact of CO₂. After they were adopted worldwide as CFC and HCFC replacements, their cumulative climate impact became impossible to ignore. The 2016 Kigali Amendment to the Montreal Protocol added HFC phase-down, and the industry is now moving toward very-low-GWP options such as HFO-1234yf, CO₂ (R-744) and propane (R-290).
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The recovery year says 2086. That is 60 years out — but I thought the Protocol was a success story?
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Both statements are true. The 1987 Montreal Protocol is the most successful environmental treaty ever, and CFC concentrations peaked in the late 1990s — that part is verified. But CFC lifetimes of 45-100 years mean that "peak" and "return to 1980 levels" are different milestones. The WMO 2022 assessment projects mid-latitude recovery around 2040, the Arctic around 2045, and the Antarctic ozone hole around 2066. Our simple "baseYear + 2τ" model gives 1986 + 90 = 2076 for CFC-11's 45-year lifetime, which is in the same ballpark. The lesson is that sustained, decades-long international cooperation is the price of recovery.
FAQ
ODP (Ozone Depletion Potential) expresses how strongly a substance destroys stratospheric ozone, relative to CFC-11 (ODP = 1.0). CFC-12 has ODP = 1.0, HCFC-22 about 0.055, Halon-1301 about 16 (very high), and HFC-134a is 0 because it contains neither chlorine nor bromine. Bromine-containing compounds tend to have particularly high ODP. This tool shows ODP per substance and uses it to compute the CFC-11 equivalent emission.
Yes. Thanks to the 1987 Montreal Protocol global controls, total stratospheric chlorine and bromine peaked in the late 1990s and have been declining since. The WMO 2018 and 2022 assessments project a return to 1980 levels around the 2030s in mid-latitudes, the 2040s in the Arctic, and roughly 2060-2070 for the Antarctic ozone hole. However, the high GWP of replacement HFCs became a separate problem, leading to the 2016 Kigali Amendment that brings HFCs under the same Protocol.
HFCs (hydrofluorocarbons) contain no chlorine or bromine, so they do not destroy stratospheric ozone (ODP = 0). However, HFC-134a has a 100-year GWP of 1,430 and HFC-23 reaches 14,800 — thousands to ten-thousands of times the warming effect of CO2. As CFCs and HCFCs were phased out, HFC use surged, making their climate impact too large to ignore. The 2016 Kigali Amendment now requires HFC phase-down (e.g., 85% reduction in developed countries by 2036).
EESC (Equivalent Effective Stratospheric Chlorine) combines the ozone-destroying contributions of chlorine and bromine into a single metric. The basic formula is EESC = [Cl] + α[Br] with α about 60, because one bromine atom destroys ozone roughly 60 times more efficiently than one chlorine atom. That is why halons reach very high ODP values even with only one or two Br atoms per molecule. The return of EESC to 1980 levels is the standard indicator for ozone-layer recovery.
Real-world applications
Refrigerant selection & HVAC design: Commercial chillers, household refrigerators, and automotive A/C all evaluate ODP and GWP under standards such as ISO 817, ASHRAE 34, and regional rules (EU F-Gas Regulation, US AIM Act, Japan's Fluorocarbon Emissions Control Law). Toggling between HFC-134a (GWP 1,430) and CFC-12 (ODP 1.0, GWP 10,900) in this tool shows why the industry is racing toward HFO-1234yf (GWP < 1) and R-744 (CO₂, GWP = 1).
Fire suppression (halon replacement): Halon-1301 has ODP 16, the highest of all common ODS, and new production was banned in 1994. Existing installations on aircraft, data centres, and ship engine rooms are being retrofitted with HFC-227ea or FK-5-1-12 (Novec 1230, ODP 0, GWP < 1). Selecting "Halon-1301" in this tool immediately shows ODP = 16, making the disproportionate destructive power obvious.
Atmospheric monitoring & modelling: WMO's Global Atmosphere Watch (GAW) and NOAA's AGAGE network measure ODS at ppt level around the world. Comparing observed concentrations against the steady-state estimate in this tool helps validate emission inventories. In 2018 an unexpected resurgence of CFC-11 was detected this way and later traced to illegal production in eastern China (Montzka et al., Nature 2018).
Climate policy assessment: The Montreal Protocol began as an ozone treaty, but it also delivers more than 10 billion tons of CO₂-equivalent mitigation per year, making it one of the most effective climate policies in existence. The CO₂-equivalent output of this tool quantifies that co-benefit per substance and per emission scenario.
Common misconceptions & caveats
The biggest misconception is that "ozone depletion and global warming are the same problem." They are not. Ozone depletion is a stratospheric chemistry effect (20-30 km altitude) that increases UV-B at the surface. Global warming is a tropospheric radiative effect from infrared absorption. However, many substances are involved in both: CFCs are ODS and potent greenhouse gases; HFCs are not ODS but are greenhouse gases; CO₂ and CH₄ are greenhouse gases but not ODS. This tool reports ODP and GWP separately to keep the two problems straight.
The second pitfall is "the Protocol fixed it, so we're safe now." CFC-11 and CFC-12 atmospheric concentrations have indeed peaked and are falling, but their long lifetimes mean recovery takes decades. Worse, an unexpected CFC-11 increase in the 2010s was traced to illegal production in eastern China (Montzka et al., 2018). Compliance monitoring is still active and depends on continued cooperation between governments, observing networks, and the atmospheric chemistry community.
Finally, "ODP = 0 means environmentally friendly" is dangerously oversimplified. HFCs and HFOs have ODP = 0 yet may have large GWPs. Natural refrigerants such as CO₂ (R-744) and propane (R-290) have negligible ODP and GWP but bring flammability, toxicity, or high-pressure design risks. In practice, refrigerant selection weighs ODP and GWP together with the ASHRAE 34 safety classification (toxicity A/B, flammability 1/2L/2/3), efficiency (COP), and cost. Use this tool as an entry point, not the final word.
How to Use
Enter annual emission rate in tonnes/year for the ozone-depleting substance (ODS)—typical values range from 0.1 to 500 tonnes/year depending on refrigerant type and facility scale
Input atmospheric lifetime in years; CFC-11 has 45 years, HCFC-22 has 12 years, and halons range from 20–65 years
Specify baseline stratospheric concentration in ppt (parts per trillion); current CFC-11 is ~240 ppt and declining
Enter the number of chlorine or bromine atoms per molecule; CFC-11 (CFCl₃) has 3 chlorine atoms, halon-1211 (CF₂ClBr) has 1 chlorine and 1 bromine
The simulator computes ODP relative to CFC-11, GWP over 100 years, CFC-11 equivalent emissions, CO₂ equivalent, and projected Montreal Protocol recovery year
Worked Example
A refrigeration plant emits 12 tonnes/year of HCFC-22 (CHClF₂). Set emission rate to 12, atmospheric lifetime to 12 years, baseline concentration to 165 ppt, and 1 chlorine atom. The simulator returns ODP = 0.055 (5.5% of CFC-11's ozone destruction), GWP = 1810 (CO₂ equivalent), atmospheric lifetime = 12 years, CFC-11 equivalent emission = 0.66 tonnes/year, and CO₂ equivalent = 21.7 Mtonnes CO₂-eq/year. Projected recovery to pre-1980 ozone levels occurs ~2070.
Practical Notes
Bromine-containing compounds (halons, methyl bromide) have ODP 5–14 times higher than chlorine equivalents; 1 kg halon-1211 (ODP = 3.0) equals ~54 kg CFC-11 in ozone impact
Atmospheric lifetime drives long-term radiative forcing; substances under 5 years (like HCFCs) have lower GWP but still damage ozone—phase-out deadlines vary by country and substance class
Use current IPCC AR6 baseline concentrations: CFC-12 ~505 ppt (2022), CFC-113 ~74 ppt; emissions data from national inventories or facility monitoring are required for regulatory reporting under the Montreal Protocol