Practical Method For Determining Safe Work While Wearing Explosive Ordnance Disposal Suits

Explosive ordnance disposal (EOD) operators wear fully encapsulating suits to protect them from potential fragments and blast while disarming or destroying threats; however, these suits impose excess heat and cardiovascular strain. This work provides a practical method for planning safe working durations of these extremely hazardous and unique activities that previously did not exist. Biophysical measures were obtained for the EOD9 suit (Med-Eng EOD9 suit, Allen Vanguard; Ottawa, Canada) using a sweating thermal manikin. An EOD9-specific mathematical model of heat transfer was developed and compared to human data from eight healthy males (age, 25.3 +/- 6.4 y; height, 180.4 +/- 6.6 cm; weight, 79.4 +/- 8.7 kg; VO2max, 57.0 +/- 5.7 ml.kg.min(-1)). Activities included three walking speeds (0.69, 1.11, and 1.53 m/s), within three environmental conditions warm-humid (WH) (ambient temperature (T-a), 32 degrees C; relative humidity (RH), 60%; mean radiant temperature, 32 degrees C), hot-dry (HD) (48 degrees C; 20%; 48 degrees C), and temperate (T) (24 degrees C; 50%; 24 degrees C). Comparisons were assessed using bias, limits of agreement (LoA), mean absolute error (MAE), and root mean square error (RMSE). Biophysical measures show EOD9 suit to be completely vapor impermeable, allowing for a simplified modeling method where evaporative cooling is completely restricted creating a strictly dry heat exchange. Averaged predicted core body temperatures possessed an acceptable bias (-0.05 degrees C), but possessed a MAE of 0.33 degrees C, RMSE of 0.42 degrees C, and LoA was -0.88 to 0.79 compared to observed data. Observed endurance times were combined with thermal modeling to provide a simple method for estimating safe working times. Simplified method can be used as a guidance for determining EOD operation planning.