Heat strain imposed by personal protective ensembles: quantitative analysis using a thermoregulation model

Area of Science:

• Occupational Health
• Human Physiology
• Protective Equipment Design

Background:

• Physical activity in protective gear can lead to heat strain.
• Understanding the impact of personal protective equipment (PPE) layers on thermoregulation is crucial for worker safety.
• Previous research has not fully quantified the independent effects of PPE mass and thermal resistance on heat strain.

Purpose of the Study:

• To investigate the impact of personal protective equipment (PPE) and its individual layers on heat strain during physical activity.
• To differentiate the effects of thermal/evaporative resistance and mass of PPE on predicted endurance time.
• To determine the contribution of specific PPE layers to overall heat strain.

Main Methods:

• Utilized a stepwise thermal manikin testing approach to evaluate a four-layer PPE ensemble.
• Employed a human thermoregulatory model to predict endurance time under various PPE configurations.
• Adjusted metabolic rates based on the mass of each PPE configuration.

Main Results:

• Wearing ballistic protection over a uniform reduced endurance time by 71 minutes (from 146 to 75 min).
• Additional resistance from ballistic protection decreased endurance by 31 minutes, while increased mass reduced it by 40 minutes.
• Both thermal/evaporative resistances and mass of PPE significantly contribute to heat strain, with comparable effects.

Conclusions:

• The mass and thermal/evaporative resistances of PPE layers, particularly ballistic and chemical protective clothing, substantially increase heat strain.
• Reducing the mass and resistance of PPE can significantly mitigate heat strain during physical activity.
• Findings provide critical data for optimizing PPE design to minimize heat strain risks.