A new quantitative method for testing performance of in-use laboratory chemical fume hoods

The American Society of Heating and Air-Conditioning Engineers (ASHRAE) 110-1995 tracer gas test method is a well-established measure of laboratory chemical hood performance, but it requires expensive equipment and trained personnel. This study proposes a new quantitative method for testing laboratory chemical fume hood performance using materials commonly found in laboratories. The method uses dry ice and warm water to generate visible fog and carbon dioxide (CO2) gas, and then measures chemical fume hood leakage with a CO2 detector. The fog can also be used as a visual aid to train workers in proper hood use. To compare the new method with the ASHRAE 110-1995 tracer gas method, both were used to test a conventional by-pass laboratory chemical fume hood under eight typical use conditions (comprised of different sash opening heights, thermal loads, and hood clutter). Average hood face velocity was maintained at 0.5 m/s (100 ft/min) ± 1% throughout all tests. The test results of the new method were comparable to those of the ASHRAE 110-1995 method. A significant regression equation was found in this study (F(1,6) = 36.15, p = 0.001), with R2 of 0.858: SF6 breathing concentration (in ppb) is equal to −118.184 + 0.912 × CO2 leakage values (in ppm). Using this regression equation, CO2 leakage can be used to estimate SF6 breathing zone concentrations. Ultimately, the new method is cheaper and easier to use than the ASHRAE 110-1995 method for routine hood performance evaluation.