Literature Review: To come to a complete understanding of heat stress it is necessary to review the science behind the body's reaction to heat stress, the various methods for measuring stress, and various methodologies used to mitigate this problem. The literature review will therefore provide an overview of knowledge on core body temperature, its regulation, heat stress, heat stress indices and the holistic approach to managing heat stress risk. The purpose of the review is to identify the research direction and methodologies employed to achieve the project objectives. The review itself is classified into the following sections: • Section-2: Humans and their behavior in the thermal environment • Section-3: Factors influencing heat stress • Section 4: Heat stress indices (used globally) • Section 5: Holistic approach to heat stress Section 2: Humans and the thermal environment This section discusses the relationship between humans and thermal environments and various factors that can influence this relationship2. 1 The concept and importance of “INTERNAL BODY TEMPERATURE” In a neutral climate, when at rest, the human body regulates its temperature at 37°C. The average temperature measured in a population in the morning after bed rest is approximately 36.7°C with a standard deviation of 0.35°C (based on data from Wenzel and Piekarski (1984)). The temperature increases during the day by approximately 0.8°C, reaching a peak in the late evening and then decreasing again in the early morning due to the circadian rhythm. This deep body temperature required for humans to maintain is approximately 370°C. Maintaining this temperature occurs through the body's response to the thermal environment. These responses could be psychological, physical... middle of paper... reduced physical work has a high potential to induce heat stress in employees engaged in such operations. Additionally, work that requires workers to wear semipermeable or waterproof protective clothing is also likely to cause heat stress among exposed workers.2.6 Metabolic RateHeat is produced in proportion to the rate of work. This deep body temperature is more closely related to metabolic rate than to the rate at which body heat must be eliminated (Nielsen, 1967). If we look at the heat stress criteria, the ISO 7243, ISO 7933 and NIOSH 1986 documents indicate that the increase in work rate could be compensated by the reduction of the environmental heat load. ISO 8996 (2004) outlines ways to determine the metabolic heat produced by the body during activities. The standard can then be applied to support the ISO 7243 standard and 7933.