Environmental Protection Agency (EPA) MVAC Certification

Which statement is true regarding HFCs and HCFCs?

1. They are stable in the atmosphere

2. They decompose when released in the lower atmosphere

3. They are more ozone-depleting than CFCs

4. They do not contribute to global warming

The correct answer is: They decompose when released in the lower atmosphere

The statement about HFCs and HCFCs indicating that they decompose when released in the lower atmosphere is true. While these compounds are indeed more stable than some other substances, they do break down under certain conditions, particularly in the photochemical reactions that occur in the atmosphere. This breakdown can lead to the formation of various byproducts, some of which can still have environmental impacts. In the context of global warming and ozone depletion, HFCs (hydrofluorocarbons) were developed as replacements for CFCs and HCFCs (hydrochlorofluorocarbons) due to their reduced ozone-depleting potential, but they can still contribute to greenhouse gas emissions. Thus, the other statements do not accurately represent the characteristics of these compounds. HFCs and HCFCs are not more ozone-depleting than CFCs, and they do have global warming potential despite being less harmful to the ozone layer than their predecessors. The stability in the atmosphere is a nuanced topic—while they are not immediately reactive, their long atmospheric lifetimes can lead to significant environmental impacts before they ultimately decompose.