HVAC Air Systems: Air Change Rates


Recirculation air change rates (ACRs) are an important factor in contamination control in a cleanroom and are the single largest factor in determining fan and motor sizing for a recirculation air handling system. Air handler sizing and air path design directly impacts the capital costs and configuration of a building. Many air change rate recommendations were developed decades ago with little scientific research to back them up. The recommended design ranges for ISO Class 5 (Class 100) cleanroom ACRs are from 250 to 700 air changes per hour.