A lightweight ambient air-cooling unit for use in hazardous environments

Area of Science:

• Environmental Physiology
• Human Factors Engineering
• Protective Equipment Technology

Background:

• Previous research confirmed intermittent conditioned air cooling effectively reduces heat storage and extends work duration for personnel in chemical defense ensembles.
• The need for enhanced thermal management strategies for individuals operating in protective gear under warm conditions is critical.

Purpose of the Study:

• To evaluate a novel continuous air-cooling strategy combining ambient air delivery during work cycles and conditioned air during rest periods.
• To assess the impact of this continuous cooling system on physiological responses, thermal comfort, and fatigue in a simulated warm environment.

Main Methods:

• A lightweight, battery-powered beltpack unit delivered filtered ambient air (5.7 L/sec) to the body and face during work cycles.
• Five experimental conditions were tested in a controlled chamber (32°C, 40% RH): no cooling (intermittent/continuous work), intermittent cooling, and continuous cooling (ambient during work, conditioned during rest).
• Physiological measures included rectal temperature, mean skin temperature, heart rate, and subjective thermal comfort and sweat evaporation assessments.

Main Results:

• Intermittent, conditioned, and continuous air cooling significantly reduced rectal temperature, mean skin temperature, and heart rate compared to no-cooling conditions.
• The continuous air-cooling strategy demonstrated significant improvements in thermal comfort and sweat evaporation.
• Continuous cooling, integrating ambient air during work and conditioned air during rest, effectively mitigated physiological strain.

Conclusions:

• A portable continuous air-cooling system, delivering ambient air during work and conditioned air during rest, enhances personal thermal comfort and reduces physiological strain.
• This approach is effective in decreasing cumulative fatigue associated with repeated work/rest cycles for individuals wearing chemical defense ensembles.
• The findings support the application of this lightweight cooling technology in military and industrial settings requiring prolonged work in protective gear under heat stress.