Determining the rate at which the air within a defined space is replaced by fresh air is a crucial aspect of indoor environmental quality. This rate, typically expressed as a numerical value representing how many times the air volume is exchanged in an hour, is achieved by dividing the volumetric flow rate of fresh air entering the space by the volume of the space itself. For example, a 100 cubic meter room with a fresh air supply of 500 cubic meters per hour has a rate of 5 air changes per hour.
Understanding and managing this exchange rate is essential for occupant health, comfort, and safety. Proper ventilation dilutes and removes airborne contaminants, such as volatile organic compounds (VOCs), carbon dioxide, and pathogens, maintaining acceptable indoor air quality. Historically, natural ventilation through windows and other openings played a primary role. However, modern building practices, with their focus on energy efficiency and sealed envelopes, necessitate the implementation of mechanical ventilation systems to achieve desired rates. Consequently, accurate assessment and control have become increasingly important in various settings, ranging from residential buildings and offices to hospitals and industrial facilities.
