A downdraft is a downward movement of air or exhaust, commonly referring to ventilation or airflow behavior in buildings.

A downdraft refers to the downward movement of air, smoke, or exhaust gases within a building or ventilation system. In construction and building systems, the term is most often used to describe airflow behavior in HVAC systems, chimneys, and kitchen ventilation.

In residential and commercial applications, downdrafts can occur when pressure differences, wind conditions, or temperature variations cause air to flow downward instead of upward. For example, chimney downdrafts can push smoke or combustion gases back into a space, while downdraft ventilation systems intentionally pull cooking fumes downward through a cooktop vent.

Managing downdraft conditions is important for indoor air quality, safety, and system performance. Proper system design, adequate makeup air, correct vent sizing, and compliance with mechanical codes help prevent unwanted downdrafts. In intentional downdraft systems, careful placement and airflow balancing are critical to ensure effective capture and exhaust.

Downdraft kitchen vents were developed to accommodate open floor plans where overhead range hoods weren’t practical or visually desirable.