Effects of work practices and upper body movements on the performance of a laboratory fume hood

A hood user's work practices and upper body movements can adversely affect the performance of a laboratory fume hood. To quantify the possible effects, hood performance was measured while simulating typical user activities scenarios. The tested variables were two sash opening heights, two hood clutter settings, two thermal loads, and three hand-arm-trunk motions, totaling 24 (2 × 2 × 2 × 3) different test conditions. Hood face velocity was maintained at 0.5 m/s for all tests, using a fan speed controller. For each test condition, the hood's performance was evaluated using the ASHRAE 110-1995 tracer gas test method. Duplicate measurements were made for each condition, so that a total of 48 tests were conducted, in random order. Three-way ANOVA was performed to find significant effects of work practices and upper body movements on breathing concentrations. The degree of sash opening was the most significant factor affecting hood performance, followed by hand-arm-trunk motions and thermal load. The effect of hood clutter was not statistically significant, but the interaction effect with other factors was. The highest breathing concentration value occurred during the test with the sash fully open, arms-down posture, thermal load present, and hood clutter present. These conditions created complex airflow patterns inside the hood that resulted in leakage into the breathing zone. Although the test conditions were limited, the results of this study suggest that good work practices in combination with good hood design and adequate face velocity can significantly reduce worker exposure. Reducing sash height while working in front of a laboratory fume hood is vital to reducing potential exposure to the air contaminant generated inside the hood.