Non-invasive sensors for core temperature estimation by heat transfer model in firefighter suits

Abstract

Firefighters are highly exposed to hyperthermia condition because firefighter suit with high heat insulation property cannot dissipate heat generated from body by firefighting activities. One of the methods to predict heat stress is to monitor esophageal temperature increase directly, however, it's almost impossible to adapt such invasive method to firefighting activities. Thereupon, we developed heat transfer mathematical model to estimate core temperature increase using non-invasive sensor in order to monitor heat stress. Sensor unit is designed to estimate heat generation by accelerometer and heat dissipation by thermometer inside firefighter suit using heat conduction model. 16 firefighters wearing firefighter protective equipment and sensor units placed inside firefighter suit walked on the treadmill in 25 degree and 40 %RH environments, and walking speed was increased by 1.5 km/h every 9 minutes after 10-minute resting state. As a result, estimated core temperature was highly correlated with measured esophageal temperature at 0.97 correlation factor.