Final answer:
Venting an 'exempt refrigerant' is legal because these substances, such as hydrocarbons, do not deplete the ozone layer and have lower global warming potential. Regulations focus on preventing the release of substances that significantly harm the ozone layer or contribute deeply to climate change. Best practices still encourage minimizing the release of all refrigerants.
Step-by-step explanation:
The question of why is venting an "exempt refrigerant" legal pertains to environmental regulations concerning refrigerants. An 'exempt refrigerant' is typically one that does not deplete the ozone layer and has lower global warming potential compared to other refrigerants. These refrigerants are often labeled as having zero ozone depletion potential (ODP) and they may include substances such as nitrogen, water vapor, neon, or hydrocarbons like propane and isobutane which have natural origins. Regulations such as the U.S.
Environmental Protection Agency's (EPA) Clean Air Act specifically prohibit the venting of ozone-depleting substances (ODS) due to their harmful impact on the ozone layer and contribution to global warming. However, substances that are not ozone-depleting and have minimal impact on climate change may be exempt from such regulations which allows for their venting during certain processes or in specific cases. It is important to note that even though venting of exempt refrigerants is legal there are still best practices that should be followed to minimize the release of any refrigerants into the atmosphere as they can still contribute to greenhouse gas emissions. Moreover even though certain refrigerants are exempt, many industries are encouraged to adopt more sustainable practices and to use refrigerants with low environmental impact.