Which type of damper closes when the mechanical ventilation system is inactive?

The correct answer is the automatic damper. Automatic dampers are designed to respond to the status of the mechanical ventilation system. When the system is not in operation, these dampers close to prevent unwanted airflow, which helps in maintaining indoor air quality and energy efficiency by minimizing drafts and heat loss when the system is off.

This is particularly important in systems that require controlled ventilation, as it ensures that conditioned air does not escape and unconditioned air does not enter when the system is inactive. Automatic dampers typically involve some form of a control mechanism, such as a spring, to ensure they close automatically when the ventilation system stops.

In contrast, other types of dampers operate differently. Flap dampers can be manually operated or spring-loaded but do not necessarily close automatically in response to the mechanical system's status. Static dampers are often used to balance airflows and do not close or open actively. Multi-zone dampers are meant to control airflow in different zones but also do not necessarily respond to system inactivity in the same way automatic dampers do.