An experimental study on the influences of air change rate and free area ratio of raised-floor on cleanroom particle concentrations

Control of indoor contaminants is a common practice in cleanroom facilities using ventilation systems with higher airflow rate. However, it is arbitrarily postulated that the ventilation systems are often over designed and are inevitably energy intensive. Several cleanroom required airflow rate model based on simplified theoretical basis have been proposed [9], [10], [11], [12], [13] and [14], but have not been thoroughly verified. This study presents an experimental investigation on the effect of room air change rate (hereafter referred as ACH) and free area ratio of raised-floor (hereafter referred as β) on particle concentration, conducted in a full-scale, non-unidirectional, raised-floor cleanroom equipped with a mini-environment facility. Four different ACHs (60, 81, 103 and 146 h−1) were evaluated with four varied β (24%, 30%, 36% and 48%) and challenge particles at 100,000 counts/ft3 (for particles with 0.1 μm in diameter). Experimental results demonstrate that the increase of ACH and β resulted in the decrease of particle concentration. Besides, the influence of β on particle concentration is more significant at low ACH cases compared to those at high ACH cases. The experimental data in this study can be a validation base for the previous proposed cleanroom required airflow rate models.

► Air change rate affects particle concentration greatly.
► The increase of the free area ratio of perforated raised-floor panels can result in lower concentrations.
► Free area ratio of perforated floor should be first considered for reducing the concentrations.