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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 (Ta), 32 °C; relative humidity (RH), 60%; mean radiant temperature, 32 °C), hot-dry (HD) (48 °C; 20%; 48 °C), and temperate (T) (24 °C; 50%; 24 °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 °C), but possessed a MAE of 0.33 °C, RMSE of 0.42 °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.

Objective: The aim of this study was to model the effect of body armor coverage on body core temperature elevation and wet-bulb globe temperature (WBGT) offset. Background: Heat stress is a critical factor influencing the health and safety of military populations. Work duration limits can be imposed to mitigate the risk of exertional heat illness and are derived based on the environmental conditions (WBGT). Traditionally a 3°C offset to WBGT is recommended when wearing body armor; however, modern body armor systems provide a range of coverage options, which may influence thermal strain imposed on the wearer. Method: The biophysical properties of four military clothing ensembles of increasing ballistic protection coverage were measured on a heated sweating manikin in accordance with standard international criteria. Body core temperature elevation during light, moderate, and heavy work was modeled in environmental conditions from 16°C to 34°C WBGT using the heat strain decision aid. Results: Increasing ballistic protection resulted in shorter work durations to reach a critical core temperature limit of 38.5°C. Environmental conditions, armor coverage, and work intensity had a significant influence on WBGT offset. Conclusion: Contrary to the traditional recommendation, the required WBGT offset was >3°C in temperate conditions (<27°C WBGT), particularly for moderate and heavy work. In contrast, a lower WBGT offset could be applied during light work and moderate work in low levels of coverage. Application: Correct WBGT offsets are important for enabling adequate risk management strategies for mitigating risks of exertional heat illness.

Purpose: We compared the accuracy and design of two thermoregulatory models, the US Army's empirically designed Heat Strain Decision Aid (HSDA) and the rationally based Health Risk Prediction (HRP) for predicting human thermal responses during exercise in hot and humid conditions and wearing chemical protective clothing. Methods: Accuracy of the HSDA and HRP model predictions of core body and skin temperature (Tc, Ts) were compared to each other and relative to measured outcomes from eight male volunteers (age 24 ± 6 years; height 178 ± 5 cm; body mass 76.6 ± 8.4 kg) during intermittent treadmill marching in an environmental chamber (air temperature 29.3 ± 0.1 °C; relative humidity 56 ± 1%; wind speed 0.4 ± 0.1 m∙s−1) wearing three separate chemical protective ensembles. Model accuracies and precisions were evaluated by the bias, mean absolute error (MAE), and root mean square error (RMSE) compared to observed data mean ± SD and the calculated limits of agreement (LoA). Results: Average predictions of Tc were comparable and acceptable for each method, HSDA (Bias 0.02 °C; MAE 0.18 °C; RMSE 0.21 °C) and HRP (Bias 0.10 °C; MAE 0.25 °C; RMSE 0.34 °C). The HRP averaged predictions for Ts were within an acceptable agreement to observed values (Bias 1.01 °C; MAE 1.01 °C; RMSE 1.11 °C). Conclusion: Both HSDA and HRP acceptably predict Tc and HRP acceptably predicts Ts when wearing chemical protective clothing during exercise in hot and humid conditions.

It is well understood that thermal strain will occur from working in hot conditions or at moderate to high work rates, and that this impact varies with wind velocity. One method for addressing the wind velocity effect on insulation and evaporative resistance includes conducting standardized thermal manikin testing followed by additional custom tests. This current method tests at the standard one wind velocity (0.4 m/s) as well as at two additional wind speeds, for a total of six tests (i.e. 3 for insulation and 3 for evaporative resistance). This process seeks to create a set of measures to produce the gradient effect of wind, in order to obtain associated coefficients. This report outlines mathematical methods for determining reasonable estimates of wind velocity effect on biophysical measures using only the standardized test methods. This new method will empower using the standard approach, for modeling purposes, while economically adding a simpler method for determining wind velocity effects.

Soldiers are particularly vulnerable to thermal strain when they are required to react to chemical, biological, radiological, nuclear, and explosive (CBRNE) threats. One solution to addressing this thermal strain is real-time physiological monitoring to improve situational and health state awareness. One proposed product is the Hidalgo, Ltd. (Cambridge, UK) Equivital EQ-02 physiological status monitoring (PSM) system. The usability and acceptability of this system has been tested previously and generally been found to be acceptable by Soldiers for military use. However, no study has examined its use in a CBRNE environment with CBRNE-PPE. This study addressed that need. A total of 28 Soldiers (26 men and 2 women) from the 22nd Chemical Battalion Technical Escort (TE), the 95th Civil Support Team Weapons of Mass Destruction (CST-WMD) and the 1st CST-WMD volunteered to participate. It was concluded that the Equivital EQ-02 system when worn under CBRNE- PPE provided utility and was comfortable to wear., Prepared in cooperation with the 95th Weapons of Mass Destruction-Civil Support Team, Hayward, CA and the 1st Weapons of Mass Destruction-Civil Support Team, Wellesley, MA.

U.S Navy submarines rarely become disabled. The first disablement and loss occurred in 1914 when leaking battery acid in USS F-4 corroded hull rivets that caused progressive flooding, chlorine off gassing, loss of depth control and eventual catastrophic hull failure. Then, after another accident in 1927 when the U.S. Submarine S-4 became disabled and was lost with all hands, rescue procedure planning, equipment and training have continuously been undergoing improvement. As a result, 12 years later, in 1939 off the shore of Portsmouth, N.H. Sailors were successfully rescued from the USS Squalus, which quickly sank after a rear compartment flooded (Stewart, 2008). The disabled Squalus was located on the sea floor at a depth of 240 ft in 29 F (-1.7 C) water, a rescue ship with a diving chamber came to the site and the 33 crew in the non-flooded compartments were transferred to the surface within 40 hours via 4 trips of the diving chamber. A major thermal hazard in such a disabling has been the threat of hypothermia from the environment caused by cold ocean water while waiting the sub s rescue (Castellani et al., 2005).

There is no debate that body armor plays an indispensible role in protecting the lives of those engaged in combat operations. However, a complex tradeoff exists between the increased survivability enabled by body armor and added weight burden that has yet to be fully understood. Soldier mobility and agility due to the added weight burden, thermal burden, and decreased agility associated with encumbering body armor. The U.S. Army has currently drafted a capabilities development document (CDD) for outlining body armor protection levels (BAPL). This work has provided a quantified assessment of the biophysical characteristics of the currently established BAPL configurations and predictive estimates for safe maximum work intensities within three environmental conditions. Predictive modeling results show a relatively linear relationship between the increased protection and increased thermal burden of BAPL configurations. The results from this work support the recommendation to continue to seek modularization to individual protection systems to allow enable tradeoff of ballistic and thermal protection.

The thermal physiological responses of military working dogs (MWD) enclosed in a kennel with a chemical protective cover were evaluated under various conditions using a thermo-physiological simulation computer model. The intent was to quantify the thermal properties of the protective kennel enclosures and to estimate the varied effects on the MWD's physiological responses, including an estimated timeline the animal can safely remain in the enclosure for given ambient meteorological conditions. More specifically, climate chamber studies of the chemical protective kennel cover were conducted over a range of environmental conditions using a human head thermal manikin with sweating capabilities to simulate the MWD. The simulations assumed that a MWD with a core temperature (Tc) of 40.5 deg C or greater experience heat-related illnesses. The simulated MWD responses indicated that a resting Belgian Malinois could remain in a covered kennel without experiencing heat-related illnesses for up to 12 h under external environmental conditions of: 30 deg C, 35 deg C and 40 deg C and 50%RH. However, if the animal is restless and moving about in the kennel, a 30 deg C outside condition could cause the dog's core temperature to approach or exceed an unsafe 40.5 deg C after about 5 hours. The study results provide guidance for safe stay times in an actively-ventilated or passively-ventilated kennel enclosed by a chemical protective cover, and illustrated the thermo-regulatory value of reducing fur length. Please note that this new MWD thermo-physiological simulation model needs to be validated and verified through laboratory and field tests with actual MWDs.