Use of a Spacer Vest to Increase Evaporative Cooling Under Military Body Armor

Abstract : U.S. military forces are currently using the Interceptor Body Armor (IBA) system which can increase human thermal stress when worn in arid environments. This study investigated a spacer vest (SV) designed to distance the IBA from the wearer's skin surface, increasing evaporative cooling around the torso. A series of lightweight SV designed to be worn under the IBA was tested for thermal insulation and water vapor permeability on a sweating thermal manikin (TM). The TM was dressed in 3 configurations: with the U.S. Army Temperate Battle Dress Uniform (TBDU); with the IBA over the TBDU; and with the IBA over the various SV and the TBDU. TM results were used as input to a computer model predicting core temperature, skin temperature, heart rate, sweat rate, skin wettedness, and total body water loss. Output described responses when exposed to desert environments with air temperatures of 30, 40 and 50 degrees C during repeated, intermittent exercise (10 min rest/ 30 min walk). TM results showed thermal insulation increased and water vapor permeability decreased when IBA was worn over the TBDU. Use of a SV between the IBA and TBDU reduced thermal insulation and increased water vapor permeability. This translated into a theoretical increase in whole body evaporative cooling potential of approximately 20% when wearing a SV compared to wearing the IBA without a SV.