Cleanrooms are one of the most energy intensive facilities per square foot. Most cleanroom airflows are determined by industry-accepted air change rates and airflow velocities. Typically, cleanroom air change rates are based upon meeting the peak particulate generation. However, these peak particulate generation time frames are relatively short and have a very short accumulated time frame during a given day, as represented on Figure 1.
Looking at Figure 1 for a typical cleanroom at constant supply airflow, the higher cleanroom particulate levels are associated with personnel entering, leaving, and working in the cleanroom. The area above the particulate level line in Figure 1 represents the times the cleanroom air-handling system is over-ventilating the space. This results in the cleanroom particulate levels dropping substantially below the maximum allowed for a particular IEST 14644-1 cleanroom cleanliness classification or owner-determined particulate level.