Tracer Gas Exposure of Human Subjects Doing Simulated Work at a Benchtop Enclosing Hood in a Wind Tunnel

Abstract

Local exhaust ventilation devices (LEV) are critical in protecting workers from harmful airborne contaminants. The aim of this study is to investigate the factors that affect the performance of a benchtop enclosing hood. A Freon 134ahelium mixture was released from a 9" diameter pie-pan placed on the floor of a 30" high by 36" wide hood at 2" from the hood face. Freon 134a was measured close to the nose and mouth for a simple manikin (unheated and not breathing), a complex manikin (heated and breathing), and ten human subjects at different times while they stood at the face of the hood in a wind tunnel. Air was drawn from probe openings at the manikin and human subjects' faces at 0.20 lpm into 5 liter sampling bags for 20 minutes each. In a factorial study design, the manikins and the human subjects were tested at hood face velocity (V face) levels from 100 to 220 fpm and wind tunnel cross-draft velocity (V cross) levels from 14 to 63 fpm. The temperature difference (∆T) between the subject's body and the environment was also recorded. The results show that V face plays an important role on subjects' exposure. In general, the exposures decreased as V face increased. A statistically significant effect (p < 0.001) of V face on log-transformed exposure at the nose and mouth (log C nose and log C mouth) was found for both the simple manikin and the human subjects; in contrast, this effect was only found on log C mouth for the complex manikin. Crossv ACKNOWLEDGMENTS This dissertation was made possible by the love and constant support of all my family members. I feel so lucky to have them in my life. I would like to thank my parents Tomás and Doris, my brothers Wilmer and Edgardo, my sister Yliana, and my nieces Yanira and Issely for their unconditional love, support, and continuous encouragement during my studies at West Virginia University. I would like to give my sincere gratitude to my research advisor and committee chair Dr. Steven Guffey for his encouragement, support, and invaluable guidance through the different stages of this project. I learned many things from his expertise in the area during many hours of conversation. I would also like to thank my research co-advisor, Dr. Ismail Celik, for his initial support for the project and his insights and encouragement in this study.