What kind of vent connection serves as a vent for both fixtures at the junction of two fixture drains?

A common vent serves as a vent for both fixtures at the junction of two fixture drains. This type of vent is specifically designed to allow multiple fixtures to share a single venting system, which can be particularly efficient in plumbing design. The common vent connects to the drain lines of both fixtures, helping to equalize pressure and prevent the potential for traps to be siphoned. This system not only improves airflow to the drainage system but also effectively minimizes the amount of space required for venting while ensuring that both fixtures operate properly without risking the creation of negative pressure or siphoning of water from drain traps.

In comparison, individual vents are dedicated vents for a single fixture, relief vents are meant to prevent backpressure in the system, and soil vents are used specifically for the discharge of waste and sewage without functioning as shared vents for multiple fixtures.