Time location analysis for exposure assessment studies of indoor workers based on active RFID technology

In this article, we describe the development of a radio frequency identification exposure monitoring system (RFEMS) suitable for tracking and identifying workers' locations in indoor workplaces. Five workers in southern Taiwan wore the RFEMS integrated into their equipment vests. Location and exposure data were transferred to data analysis software for visualization and tabular analysis in real-time. Data were grouped into seven task activity location categories to determine the time spent and percentage reception in each location. The RFEMS could also synchronously indicate the surrounding conditions using various sensors. Additional experiments were focused on locating of boundaries and determining the instrument stability, power sustainability, and reception efficiency in typical environments. The RFEMS instruments provided adequate range for locating (typically ca. 6-45 m in each zone), allowing us to locate subjects within distinct microenvironments and to distinguish between the activities of a variety of workers, the average time activity pattern (TAP) recording deviation for both human observations and RFEMS was ca. 0.21-1.57%. Power consumption experiments revealed that the system could be sustained for more than 124 h. A pilot field test indicated that the RFEMS offers a new level of accuracy for direct quantification of time activity patterns in exposure assessments of indoor workers over long periods of time.