Measuring heat stress

• Wet Bulb Globe temperature index
• Estimating Metabolic Rate
• Physiological Monitoring
• Estimating Clothing Insulation Values

There are three types of method used for the assessment of hot environments:

• Empirical – Uses laboratory data to predict the likely effects an environment will have on a human, (ie physiological responses); enabling predictions to be made that estimate work rate, metabolic rate, clothing factors etc.
• Direct - Standardised instruments measure environmental parameters eg globe temperature
• Rational - Calculations of the heat exchanges between the employee and the work environment provides a method for predicting employees responses.

The purpose of these methods is to estimate or establish the physiological responses of an individual to their environment.  The end result is to provide a value which allows a comparison between environments, different working situations and different types of clothing to be made.

Obtaining thermal stress indices requires four processes to occur:

• Input Values - enabling calculations to be made from direct measurement or by extrapolation.
• Calculations
• Output Values: - the results from the calculations.
• Interpretations: - of the outputs either by using a heat stress index, the user or both