Recirculation is associated with which form of ventilation?

Recirculation is primarily associated with negative-pressure ventilation because this method creates a pressure differential that draws air into the space from surrounding areas. In negative-pressure ventilation, the removal of air from the environment creates a vacuum effect, which can cause outside air to be drawn into the space. This air movement can lead to recirculation of smoke, heat, and hazardous gases within the structure if not properly managed, as the flow of fresh air can mix with the contaminants being expelled.

Negative-pressure ventilation is often used in firefighting to vent smoke and heat from an affected area, although care must be taken to ensure that the recirculated air does not further endanger firefighters or victims. Understanding the dynamics of this form of ventilation is crucial for effective strategies and tactics in firefighting situations.