Dependence of ESD charge voltage on humidity in data centers: Part II - Data analysis

This is Part II of a three-part paper investigating the dependence of charge voltage generated by human activity on humidity in data centers. The first paper described the experimental methods, while this paper is devoted to the analysis of the electrostatic charge voltage levels along the following parameters: relative humidity, absolute humidity, footwear, flooring, and type of activity. The human activities studied included well-defined walking, random walking, taking off and dropping a sweater, and standing up from a chair. This study confirms the importance of footwear and flooring and quantifies their effectiveness. The results indicate that lower absolute humidity may not always lead to higher voltages, while reducing the relative humidity will cause the average voltages to increase. The high voltages, created by removing and dropping a sweater and by standing up from a chair, indicate that these types of user activities might pose a higher ESD (electrostatic discharge) risk (generating voltage greater than 6 kV) than the walking activities. The analyses are based on the definition of walking, standing, chair event, and sweater event voltages, as presented in Part I.