HVAC Air Systems: Demand-controlled Filtration


Recirculation air flow in cleanrooms has traditionally been determined through various methods. There are several published recommended ranges of airflow which present differing recommendations including ASHRAE Applications Handbook chapter 16 (Table 2), IEST Recommended Practice 012.1, and ISO 14644-4 Annex B, however, these and other sources provide conflicting recommended ranges of air change rates and the range of values is very broad. Air change rates have been determined based upon historical rules of thumb, that which was previously successful for similar contamination control situations, or pure guesswork.