This indicator is used to monitor the reduction in the usage of Ozone Depleting Substances (ODSs) as a result of the Montreal Protocol. Therefore only ODSs controlled under the Montreal Protocol are covered by the indicator. Reducing consumption ultimately leads to reductions in emissions since most uses of ODSs finally lead to the substances being emitted into the atmosphere. The Units of Measurement are metric tons of ODS weighted by their Ozone Depletion Potential (ODP), otherwise referred to as ODP tons. Ozone depleting potential (ODP) refers to the amount of ozone depletion caused by a substance. It is the ratio of the impact on ozone of a chemical substance compared to the impact of a similar mass of CFC-11. The ODP of CFC-11 is defined to be 1. CFCs have ODPs that range from 0.6 to 1 while hydrochlorofluorocarbons (HCFCs) have ODPs that range from 0.001 to 0.52. The halons have ODPs of up to 10 while methyl bromide has an ODP of 0.6.

Source: UNEP