Development and validation of the predicted heat strain model

Area of Science:

• Occupational Health and Safety
• Environmental Physiology
• Ergonomics

Background:

• Existing methods for assessing workplace heat stress, such as the Required Sweat Rate model (ISO 7933:1989), require review and improvement.
• Coordinated European research efforts are crucial for advancing the understanding of thermal factors in occupational settings.
• Accurate assessment of heat disorders is vital for protecting worker health in hot environments.

Purpose of the Study:

• To review the scientific basis of the ISO 7933 standard for heat stress assessment.
• To develop and validate an improved model for predicting heat strain in occupational settings.
• To enhance the accuracy of predicting physiological responses to heat exposure, including sweat rate and core body temperature.

Main Methods:

• A collaborative research project involving eight European laboratories was conducted.
• A revised model, the Predicted Heat Strain (PHS) model, was developed based on a thorough review of existing standards.
• The PHS model was validated against 909 laboratory and field experiments, comparing predicted sweat rates and rectal temperatures with observed data.

Main Results:

• The PHS model demonstrated strong predictive accuracy, with Pearson correlation coefficients of 0.76 (sweat rate, lab) and 0.74 (sweat rate, field).
• Predictions for rectal temperature also showed good correlation (0.66 for lab, 0.59 for field).
• The PHS model showed improved accuracy in predicting the change in sweat rate over time compared to the Required Sweat Rate model.

Conclusions:

• The Predicted Heat Strain (PHS) model offers a more accurate tool for assessing heat strain in occupational environments.
• The PHS model provides a better basis for determining safe exposure limits by predicting dehydration and core temperature increases.
• This research contributes to improved occupational safety standards for managing heat stress in the workplace.