Air change rate, a measure of ventilation effectiveness, is expressed as the number of times the air within a defined space is replaced per hour. This metric quantifies the rate at which outside air is introduced and stale air is removed from a room or building. For example, a rate of one indicates the entire volume of air is replaced once every hour.
Maintaining adequate air exchange is vital for indoor environmental quality. It plays a crucial role in diluting pollutants, controlling humidity, and maintaining comfortable temperatures. Historically, achieving sufficient ventilation relied on natural means like open windows, but contemporary building design often necessitates mechanical systems for consistent and controlled air exchange.