International heat stress standards: a review

Heat stress indices are included in international standards to provide methods and limits for the design, assessment and control of hot thermal environments. Indices used in standards are described with particular reference to those in ISO standards concerned with the ergonomics of the thermal environment. ISO 7243 provides a simple method for assessing and controlling hot environments based upon the WBGT (web bulb globe temperature) index. ISO 7933 describes an analytical method of assessment of hot environments based upon the human heat balance equation and the calculation of the required sweat rate index (Sreq). This standard is discussed in detail with particular consideration of its use in practical application. The method has been evaluated in both laboratory and industrial contexts. Limitations of the standards and areas where further development is required, are presented.