Atmosphere and chemicals
Ozone-Depleting Substance (ODS)
Chemicals such as CFCs and halons that destroy stratospheric ozone, controlled and largely phased out under the Montreal Protocol.
Definition
Ozone-depleting substances are human-made chemicals — including chlorofluorocarbons (CFCs), halons, carbon tetrachloride, methyl chloroform, hydrochlorofluorocarbons (HCFCs) and methyl bromide — that release chlorine or bromine in the stratosphere, destroying ozone. Their production and consumption are controlled under the Montreal Protocol, which has achieved near-total phase-out of the main ODS.
References
controlled substances and phase-out framework
substance categories and uses
Overview
What it means
Used historically in refrigeration, air conditioning, foams, aerosols, solvents and fire suppression, ODS accumulate in the stratosphere where a single chlorine atom can destroy thousands of ozone molecules.
The Montreal Protocol's control schedules, with differentiated timelines for developing countries, drove substitution to alternatives — some of which (HFCs) are potent greenhouse gases now being phased down under the Kigali Amendment.
How it is used
The term is central to ozone and climate policy, customs enforcement against illegal ODS trade, and servicing-sector regulation; UNEP's Ozone Secretariat tracks compliance.
Why it matters
ODS control is the most successful global environmental regime to date: the ozone layer is healing, with recovery expected around mid-century, and the phase-out has also avoided substantial climate warming.
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