Which of the following substances is NOT covered by the Montreal Protocol?

The Montreal Protocol is an international treaty focused on phasing out substances that deplete the ozone layer. The treaty specifically targets chlorofluorocarbons (CFCs), halons, and various other ozone-depleting chemicals.

The correct answer highlights that the substances not covered by the Montreal Protocol are those that do not have an ozone-depleting potential. Chemicals that do not harm the ozone layer, by definition, are not included in the treaty's regulations since the primary goal of the Montreal Protocol is to protect stratospheric ozone by eliminating harmful substances.

Therefore, options such as CFCs, halons, and methyl chloroform are all substances specifically addressed by the protocol due to their known harmful effects on ozone. In contrast, a chemical that does not contribute to ozone depletion falls outside the scope of the Protocol's regulations. This distinction is crucial in understanding the objectives and coverage of the Montreal Protocol in relation to environmental health and safety standards.