A real-time heat strain index using foot temperature and heart rate while wearing personal protective equipment in hot environments

Abstract

Over the past century, a number of indices to assess heat stress and strain in hot environments have been developed, but there are few non-invasive indices to evaluate the heat strain of workers wearing personal protective equipment. ISO 7933 [1] presents an analytical method to determine heat stress using calculation of the predicted heat strain but the calculation is complicated to apply for real-time monitoring. Moran and colleagues [2,3] derived a simple and useful index based on rectal temperature (Tre) and heart rate (HR) (Physiological Strain Index, PSI) but the index is limited at work in fields because of the direct measurement of rectal temperature. The purpose of this study was to present a non-invasive method to monitor heat strain in real-time using foot temperature (Tfoot) and HR of workers wearing personal protective equipment with protective boots in hot environments.