Performance of Painting Booths Equipped with Down-Draft Ventilation

Abstract

A study to evaluate the performance criteria of painting booths equipped with down-draft ventilation investigated 15 painting booths, studying 5 groups of characteristics: configuration of booths, ventilation parameters, paint-application parameters, environmental conditions, and contaminant levels. Results demonstrated the potential for significant occupational exposure to isocyanates and the existence of significant variations in the ability of down-draft ventilation systems to eliminate these contaminants. Correlations of weighted isocyanate concentrations in the ambient air and in breathing zones with ventilation parameters demonstrated that the air velocity and turbulence of both ambient and breathing-zone air were the principal determinants of the concentrations of oligomeric isocyanates, i.e., isocyanates present as particulates. For monomeric isocyanates, and gaseous contaminants generally, the extraction rate and turbulence were the most important factors. These results indicate that the performance of paint-booth ventilation systems depends on the presence of vertical air flow, and that the ventilation parameters with the greatest effect on performance are air velocity, flow direction, and flow homogeneity. Regression analysis was used to propose turbulence and velocity values and a booth configuration to obtain these values.