Cleanroom air quality: combined effects of ventilation rate and filtration schemes in a laboratory cleanroom
Mohammad Saleh Nikoopayan Tak, Arup Bhattacharya, A. R. Metcalf, Ehsan Mousavi
Abstract
Ventilation performance and air quality in cleanrooms are affected by several interconnected parameters, and a change in one component can impact the entire system. Furthermore, occupant interactions with the physical environment can influence particle dispersion, disrupt current airflow by introducing new wakes and ultimately decrease ventilation efficacy. As a result, we set up an experimental study to measure the effects of traffic, flowrate and filtration on ventilation performance while a source of contamination was inside the room. Experiments included three types of occupant movements (i.e., NM, WO, WT) and were performed under two different airflow conditions. Three different metrics, namely relative ventilation efficiency ((ϵjt)), decay rate (R) and exposure (γ), were introduced to statistically compare changes in ventilation performance in response to different experimental setups. Decay rates obtained for 0.3-micron particles decreased by up to 50% in the presence of occupants. Lowering cleanroom flowrate due to additional filtering can reduced ventilation effectiveness by almost 50%. Care should be exercised when changing filter efficiency because it can reduce the rate of air supply. These findings are especially intriguing in the context of cleanroom retrofit, as reducing air exchange rates was an unintended consequence of improving filter efficiency.