The purpose of this study is to quantitatively evaluate hood leakage by measuring face velocity and to introduce screening tools with smoke tubes and smoke matches for hood leakage during a volume generating process that simulates a hot process, defined here as any operation producing high temperature gases. A literature search reveals that during the last couple of decades only Johnson et al. reported a quantitative linear relationship between thermal loading and breathing zone trace gas concentrations using ASHRAE 110-1995 method. Hot processes may well be the most common and least recognized of the operational factors able to cause fume hoods to leak. Smoke tests and face velocity tests were conducted for hood performance testing. Smoke tests were executed by means of smoke tubes and smoke matches as screening tools for hood leakage. ace velocity tests were conducted at 16 points arranged to represent equal areas of the hood face when the sash was fully opened. Through smoke tests and a volume generating process, unexpected leakage above the fume hood was found through smoke testing and at the face of fume hood. These results suggest that when a hood is operated with any operation producing high temperature gases, leakage can be caused. This study shows that if there is any fume hood experiment with high temperature or able to cause fume hood to leak, the fume hood must be controlled with stable face velocity using a damper to protect workers and engineers from hazardous gases released within it.
The goal of fume hood testing is to determine how well the hood protects the laboratory worker from the hazardous substances released within it. A hot process, defined here any operation producing high temperature gas, has been recognized as a causal factor in the leakage of contaminants from laboratory fume hoods since 1950. A volume generating process is a simulation for a hot process. Schulte et al. found appreciable smoke leakage driven by a hot process in a fume hood. Several articles relied on smoke tests to qualitatively relate thermal loading to leakage. F.H. Fuller reported heat-induced leakage through cracks, seams, and openings in the hood structure. With ASHRAE 110-1995 tracer gas testing, Johnson et al. found quantitative correlation between heat output and emissions. Maupins et al. found the tracer gas test of fume hood leakage to be representative of relative employee exposure in a survey of 46 chemical fume hoods. A literature search reveals that during the last couple of decades only Johnson et al. reported a quantitative linear relationship between thermal power of a hot process and trace gas concentrations of breathing zone. Hot processes may well be the most common and least recognized of the operational factors able to cause fume hoods to leak.
