This arrangement is called gravity, or buoyancy-driven, ventilation; warm air rises and generates an updraft in a central ventilation conduit connected to an ou

This arrangement is called gravity, or buoyancy-driven, ventilation; warm air rises and generates an updraft in a central ventilation conduit connected to an outlet vent in each unit. The replacement air is “sucked in” through an inlet, also in each apartment. It’s used in multi-story buildings everywhere, but it’s not as effective in lowrises. It can be boosted by having mechanical ventilation equipment on the roof – a rooftop ventilator – pulling air through the exhaust flue more effectively, and modern apartment buildings typically have this type of mechanical ventilation. (So even if your apartment only has a passive vent in the wall, that doesn’t necessarily mean the entire system is passive!) Today, the inlets may also be centralized; this allows for replacement air to be taken from wherever it’s the cleanest, eg. from the side not adjacent to a street. The air can also be filtered to improve its quality and even pre-heated to make heating more efficient and prevent the feeling of a draft.