The Montreal Protocol on Substances that Deplete the Ozone Layer

The Montreal Protocol on Substances that Deplete the Ozone Layer is a global agreement to protect the Earth’s ozone layer by phasing out the chemicals that deplete it. This phase-out plan includes both the production and consumption of ozone-depleting substances. The landmark agreement was signed in 1987 and entered into force in 1989.

The parties to the Protocol meet once a year to make decisions aimed at ensuring the successful implementation of the agreement. These include adjusting or amending the Protocol, which has been done six times since its creation. The most recent amendment, the Kigali Amendment, called for the phase-down of hydrofluorocarbons (HFCs) in 2016. These HFCs were used as replacements for a batch of ozone-depleting substances eliminated by the original Montreal Protocol. Although they do not deplete the ozone layer, they are known to be powerful greenhouse gases and, thus, contributors to climate change.

The Montreal Protocol provided a set of practical, actionable tasks that were universally agreed on. The Protocol has successfully met its objectives thus far and continues to safeguard the ozone layer today. Thanks to the collaborative effort of nations around the world, the ozone layer is well on its way to recovery.

Annex C: Controlled substances

Group Substance Number of isomers Ozone-Depleting Potential* 100-Year Global Warming Potential***
Group I        
CHFCl2 (HCFC‑21)** 1 0.04 151
CHF2Cl (HCFC‑22)** 1 0.055 1810
CH2FCl (HCFC‑31) 1 0.02  
C2HFCl4 (HCFC‑121) 2 0.01–0.04  
C2HF2Cl3 (HCFC‑122) 3 0.02–0.08  
C2HF3Cl2 (HCFC‑123) 3 0.02–0.06 77
CHCl2CF3 (HCFC‑123)** – 0.02  
C2HF4Cl (HCFC‑124) 2 0.02–0.04 609
CHFClCF3 (HCFC‑124)** – 0.022  
C2H2FCl3 (HCFC‑131) 3 0.007–0.05  
C2H2F2Cl2 (HCFC‑132) 4 0.008–0.05  
C2H2F3Cl (HCFC‑133) 3 0.02–0.06  
C2H3FCl2 (HCFC‑141) 3 0.005–0.07  
CH3CFCl2 (HCFC‑141b)** – 0.11 725
C2H3F2Cl (HCFC‑142) 3 0.008–0.07  
CH3CF2Cl (HCFC‑142b)** – 0.065 2310
C2H4FCl (HCFC‑151) 2 0.003–0.005  
C3HFCl6 (HCFC‑221) 5 0.015–0.07  
C3HF2Cl5 (HCFC‑222) 9 0.01–0.09  
C3HF3Cl4 (HCFC‑223) 12 0.01–0.08  
C3HF4Cl3 (HCFC‑224) 12 0.01–0.09  
C3HF5Cl2 (HCFC‑225) 9 0.02–0.07  
CF3CF2CHCl2 (HCFC‑225ca)** – 0.025 122
CF2ClCF2CHClF (HCFC‑225cb)** – 0.033 595
C3HF6Cl (HCFC‑226) 5 0.02–0.10  
C3H2FCl5 (HCFC‑231) 9 0.05–0.09  
C3H2F2Cl4 (HCFC‑232) 16 0.008–0.10  
C3H2F3Cl3 (HCFC‑233) 18 0.007–0.23  
C3H2F4Cl2 (HCFC‑234) 16 0.01–0.28  
C3H2F5Cl (HCFC‑235) 9 0.03–0.52  
C3H3FCl4 (HCFC‑241) 12 0.004–0.09  
C3H3F2Cl3 (HCFC‑242) 18 0.005–0.13  
C3H3F3Cl2 (HCFC‑243) 18 0.007–0.12  
C3H3F4Cl (HCFC‑244) 12 0.009–0.14  
C3H4FCl3 (HCFC‑251) 12 0.001–0.01  
C3H4F2Cl2 (HCFC‑252) 16 0.005–0.04  
C3H4F3Cl (HCFC‑253) 12 0.003–0.03  
C3H5FCl2 (HCFC‑261) 9 0.002–0.02  
C3H5F2Cl (HCFC‑262) 9 0.002–0.02  
C3H6FCl (HCFC‑271) 5 0.001–0.03  
       
Group Substance Number of isomers Ozone-Depleting Potential*
Group II      
CHFBr2   1 1.00
CHF2Br (HBFC-22B1) 1 0.74
CH2FBr   1 0.73
C2HFBr4   2 0.3-0.8
C2HF2Br3   3 0.5-1.8
C2HF3Br2   3 0.4-1.6
C2HF4Br   2 0.7-1.2
C2H2FBr3   3 0.1-1.1
C2H2F2Br2   4 0.2-1.5
C2H2F3Br   3 0.7-1.6
C2H3FBr2   3 0.1-1.7
C2H3F2Br   3 0.2-1.1
C2H4FBr   2 0.07-0.1
C3HFBr6   5 0.3-1.5
C3HF2Br5   9 0.2-1.9
C3HF3Br4   12 0.3-1.8
C3HF4Br3   12 0.5-2.2
C3HF5Br2   9 0.9-2.0
C3HF6Br   5 0.7-3.3
C3H2FBr5   9 0.1-1.9
C3H2F2Br4   16 0.2-2.1
C3H2F3Br3   18 0.2-5.6
C3H2F4Br2   16 0.3-7.5
C3H2F5Br   8 0.9-1.4
C3H3FBr4   12 0.08-1.9
C3H3F2Br3   18 0.1-3.1
C3H3F3Br2   18 0.1-2.5
C3H3F4Br   12 0.3-4.4
C3H4FBr3   12 0.03-0.3
C3H4F2Br2   16 0.1-1.0
C3H4F3Br   12 0.07-0.8
C3H5FBr2   9 0.04-0.4
C3H5F2Br   9 0.07-0.8
C3H6FBr   5 0.02-0.7
       
Group III      
CH2BrCl bromochloromethane 1 0.12

* Where a range of ODPs is indicated, the highest value in that range shall be used for the purposes of the Protocol. The ODPs listed as a single value have been determined from calculations based on laboratory measurements. Those listed as a range are based on estimates and are less certain. The range pertains to an isomeric group. The upper value is the estimate of the ODP of the isomer with the highest ODP, and the lower value is the estimate of the ODP of the isomer with the lowest ODP.

** Identifies the most commercially viable substances with ODP values listed against them to be used for the purposes of the Protocol.

*** For substances for which no GWP is indicated, the default value 0 applies until a GWP value is included by means of the procedure foreseen in paragraph 9 (a) (ii) of Article 2.