What distinguishes a vapor vent from other types of vents?

A vapor vent is specifically designed to release various gases outside of a plumbing system. This function is crucial because, during the operation of plumbing fixtures and appliances, gases such as sewer gases can accumulate. The vapor vent prevents these gases from building up within the system and allows them to escape safely into the atmosphere, which is essential for maintaining health and safety standards.

The other options do not accurately describe the principal function of a vapor vent. Conducting air into the system is typically the role of an air vent, which allows for necessary airflow to prevent siphoning effects and maintain proper drainage. The notion of only releasing hot air does not cover the broader purpose of releasing different types of gases, making the characterization too narrow. Similarly, a vapor vent does not serve the purpose of preventing backflow; that function is usually fulfilled by devices known as backflow preventers, which are designed to prevent contaminated water from re-entering the potable water supply.