A novel method to evaluate safe heat exposure distance for firefighters under thermal radiation conditions

Abstract

Background Correct evaluation of safe heat exposure distance (SHED) in wildland fire environments improves the safety and efficiency of firefighting operation. However, there is a lack of standard test method for the SHED, let alone the influencing factors of the SHED. Aims The aim of this study was to develop a novel method to examine the SHED by considering clothing and fire factors under thermal radiation condition. Methods We developed a new experimental apparatus for evaluating the SHED of firefighters in fire environments. The testing accuracy and repeatability was verified by calibration and measurement results. The evaluation method was used to investigate the influences of heating source temperature and fabric combination on the SHED, and reveal the relationship between the SHED and safe heat exposure time (SHET). Key results The results showed that there was a significant positive correlation between the heating source temperature and the SHED. When the heating source temperature increased from 200 to 550°C, the SHED of three single-layer fabrics increased by more than 1.23 times. The SHED was negatively correlated with the reflectance, grammage and thickness of the fabric. The SHET increased with the heating source distance, and the rising rate increased gradually. Implications The findings obtained in this study can be used to provide theoretical support for determining the SHED during fire rescue, and to help engineer clothing that provides higher protection for firefighters.