Assessment of Air Change Rates in Chemical Laboratories

Abstract

By performing a set of controlled experiments and field measurements, this study investigated ventilation conditions in chemical laboratories in universities, as well as the impact of various ventilation measures on air change rate (ACR). The controlled study was conducted in one research laboratory. On/off air-conditioning, a fume hood, local exhaust, and an open door were the test variables. The field study measured ACR in 24 chemical laboratories at two universities. Ventilation in each laboratory was assessed by estimating the ACR using CO2-decay approaches. Controlled study results indicate that air-conditioning and local exhaust did not significantly impact the ACR, whereas use of a chemical hood or open door significantly ( p < 0.05) increased the ACR by 4.6- and 3.2-fold, respectively. Field measurements indicate that the average ACR for laboratories with air-conditioning and closed windows, air-conditioning with windows partially closed, and no air-conditioning with windows open and fans were 2.18, 10.1, and 23.8 (h-1), respectively. Overall, 38% of chemical laboratories measured in this study, especially those using air-conditioning with closed windows (∼100%), did not meet the Occupational Safety and Health Administration laboratory ventilation requirements of four air exchanges per hour. Opening windows, at least partially, improved the ACR.