Inside the 'Hurt Locker': The Combined Effects of Explosive Ordnance Disposal and Chemical Protective Clothing on Physiological Tolerance Time in Extreme Environments.

Background: Explosive ordnance disposal (EOD) technicians are often required to wear specialized clothing combinations that not only protect against the risk of explosion but also potential chemical contamination. This heavy (>35kg) and encapsulating ensemble is likely to increase physiological strain by increasing metabolic heat production and impairing heat dissipation. This study investigated the physiological tolerance times of two different chemical protective undergarments, commonly worn with EOD personal protective clothing, in a range of simulated environmental extremes and work intensities

Methods: Seven males performed 18 trials wearing 2 ensembles. The trials involved walking on a treadmill at 2.5, 4, and 5.5 km h(-1) at each of the following environmental conditions, 21, 30, and 37°C wet bulb globe temperature. The trials were ceased if the participants' core temperature reached 39°C, if heart rate exceeded 90% of maximum, if walking time reached 60min or due to volitional fatigue.

Results: Physiological tolerance times ranged from 8 to 60min and the duration (mean difference: 2.78min, P > 0.05) were similar in both ensembles. A significant effect for environment (21 > 30 > 37°C wet bulb globe temperature, P < 0.05) and work intensity (2.5 > 4 > 5.5 km h(-1), P < 0.05) was observed in tolerance time. The majority of trials across both ensembles (101/126; 80.1%) were terminated due to participants achieving a heart rate equivalent to greater than 90% of their maximum.

Conclusions: Physiological tolerance times wearing these two chemical protective undergarments, worn underneath EOD personal protective clothing, were similar and predominantly limited by cardiovascular strain.