Ans. The main ozone-depleting substances (ODS) responsible for the ozone hole are chlorofluorocarbons (CFCs) and halons. CFCs were widely used in the past as refrigerants, aerosol propellants, and foam-blowing agents. Halons were primarily used in fire extinguishing systems. These substances contain chlorine and bromine atoms, which are released into the stratosphere upon their release into the atmosphere. Once in the stratosphere, these ODS undergo chemical reactions that ultimately lead to the destruction of ozone molecules.