Evaluation of Ventilation Designs for Increasing Local Exhaust Ventilation Performance in Traditional Settings and Concrete Dowel Drilling

Abstract

Over 2 million workers are potentially exposed to respirable crystalline silica with the overwhelming majority in the construction industry. Occupational exposure to respirable crystalline silica can lead to silicosis, lung cancer, and other adverse diseases. The present research evaluated novel designs in both traditional ventilation and local exhaust ventilation for a concrete dowel drill to reduce occupational exposures such as silica. The first study investigated traditional ventilation novel designs to increase capture velocities without increasing fan speeds or power consumption. The second and third study focused on improving a concrete dowel drill local exhaust ventilation design to reduce potential respirable crystalline silica exposures during large concrete construction project such as airport runways. Previous research indicated that the manufacturer’s local exhaust ventilation system reduced respirable crystalline silica exposures by over 90 percent but the system was susceptible to filter and hose clogging which reduced performance. In the second study, a laboratory study evaluated two novel local exhaust ventilation hoods, one commercially available hood, and the dowel drill manufacturer’s hood for hood efficiency and airflow characteristics. The novel design hoods increased hood coefficient of entry from 0.59 for the manufacturer’s hood to 0.64 indicating increased efficiency. Novel simple hood analysis found an average hood coefficient of entry of 0.81 indicating further improvements can be made. In the third study, simulated workplace conditions were used to evaluate the best performance hood identified in laboratory testing along with other local exhaust ventilation modifications such as replacing the manufacturer’s corrugated hose with smooth-bore hose and including a cyclone pre-separator to reduce the dust transport burden within the exhaust system. The most effective local exhaust ventilation configuration consisted of the novel design hood, smooth-bore hose, and cyclone which reduced average accumulated hose weight (manufacturer’s configuration = 0.3 pounds per trial vs. most effective configuration = 0.05 pounds per trial) and increased average cleanout bucket capture (0.95 pounds per trial to 6.30 pounds per trial). These metrics indicated potential concrete dowel drill ventilation system efficiency and capture performance increases that address the ventilation system limitations indicated by previous research.PhDEnvironmental Health SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133420/1/couchjr_1.pd