What are widely used in the refrigeration, foam, solvent, aerosol and firefighting sectors as a transitional substance to substitute CFCs?

• A. SF6
• B. HFCs
• C. Halons
• D. HCFCs

Answer: (D)

This question is about substitutes designed to replace CFCs in common industry uses while keeping the transition manageable. HCFCs were chosen as transitional substitutes because they behave similarly to CFCs in refrigeration, foam blowing, solvents, aerosols, and firefighting, but they release far less chlorine in the atmosphere, so their ozone-depleting potential is much lower. This allowed industries to continue using familiar equipment and processes while the world phased out CFCs under the Montreal Protocol, giving time to move toward even safer, lower-GWP options. It’s important to note that HCFCs still have some ozone-depleting potential, so they’re being phased down themselves, but they served as the practical stepping stone. Other options don’t fit this transitional role: SF6 has no ozone depletion concern but is a potent greenhouse gas and not used to replace CFCs in those sectors; Halons are ozone-depleting and largely restricted; HFCs are newer replacements with zero ozone depletion potential but were not the initial transitional substitutes in these sectors.