Determining the rate at which the air within a defined space is replaced with fresh air involves a specific formula. This typically involves dividing the airflow rate, often measured in cubic feet per minute (CFM), by the volume of the space, measured in cubic feet, and then multiplying by 60 to express the result in air changes per hour (ACH). For example, a 1,000 cubic foot room with an airflow rate of 500 CFM would have an ACH of 30. Understanding this metric is essential for assessing ventilation effectiveness.
Maintaining a sufficient rate of air exchange is critical for indoor air quality (IAQ) and occupant well-being. Proper ventilation helps dilute and remove airborne contaminants such as volatile organic compounds (VOCs), particulate matter, and pathogens. This is particularly important in settings like hospitals, laboratories, and industrial facilities where specific air quality standards must be met. Historically, the importance of ventilation was recognized even before modern understanding of airborne diseases, with natural ventilation strategies employed in building design for centuries.