Which substance can substitute for ozone-depleting chemicals?

• A. Hydrofluorocarbons
• B. Chlorofluorocarbons themselves
• C. Ammonia
• D. Sulfur hexafluoride

Answer: (A)

Substituting ozone-depleting chemicals relies on choosing substances that don’t release chlorine or bromine into the atmosphere, because those elements drive the breakdown of stratospheric ozone. Hydrofluorocarbons fit this need well—they were designed to replace chlorofluorocarbons by providing similar performance in applications like refrigeration and foam production while not containing chlorine or bromine, so they don’t contribute to ozone depletion. In contrast, chlorofluorocarbons themselves are the very substances that harm the ozone layer, so they aren’t substitutes. Ammonia isn’t a standard substitute in many ozone-depleting contexts due to toxicity and other handling concerns, and sulfur hexafluoride is mainly used for electrical insulation and also isn’t a typical substitute for the kinds of ozone-depleting chemicals in consumer products, even though it doesn’t deplete ozone.