aircirculation

Air circulation refers to the movement and distribution of air within a space or region. It results from temperature differences, pressure gradients, and external forces such as wind or mechanical fans. Effective air circulation influences thermal comfort, humidity distribution, and the transport or dilution of airborne contaminants.

In the atmosphere, circulation is driven by solar heating that creates rising warm air and sinking cooler air. This generates large-scale cells, including Hadley, Ferrel, and Polar cells, as well as jet streams and prevailing winds. Localized circulation, such as breezes near coasts or urban areas, shapes weather and climate patterns.

Indoor air circulation combines ventilation and diffusion within rooms. Ventilation exchanges indoor air with outdoor air, either naturally through openings or mechanically with fans and ductwork. Mixing by heating, ventilation, and air conditioning systems distributes air to prevent stagnation and to control temperature and humidity.

Factors influencing indoor circulation include room geometry, vent placement, door and window positions, occupancy, outdoor air quality, and thermal stratification. Poor circulation can cause stagnation, uneven temperatures, and accumulation of carbon dioxide, humidity, odors, or volatile organic compounds, while excessive drafts can reduce comfort and energy efficiency.

Design and operation of buildings seek to optimize air circulation for safety, comfort, and efficiency. Measurement methods include tracer gas tests, anemometry, and computational fluid dynamics simulations. Outdoor air quality and weather conditions interact with indoor circulation to determine overall air quality.