A circuit vent is defined as:

A circuit vent is defined as a branch vent that serves two or more floor outlet fixtures. This is significant because it allows for the proper ventilation of multiple fixtures that are connected to a common drainage system, ensuring that gases and odors do not accumulate within the plumbing system.

The unique design of a circuit vent provides an efficient way to ventilate more than one fixture in a horizontal branch, which can be especially useful in configurations where multiple fixtures are closely located, such as in bathrooms. By installing a circuit vent, plumbing professionals can enhance the overall effectiveness of the venting system, preventing issues like siphoning and maintaining a proper airflow through the drainage system.

This is contrasted with other concepts, such as a vent for one fixture only or a main vent for newly constructed buildings, which focus on more limited applications. Additionally, the option of a vent specifically used for hot water systems does not accurately describe the purpose and function of a circuit vent, as circuit vents are not exclusive to hot water systems.