ABSTRACT
Of all of the heat stress indices, the wet-bulb globe temperature (WBGT) index is the most widely accepted and used throughout the world. It is a simple direct index based upon the weighted average of temperatures. It all started around the early 1950s in the United States when a commander in the US Navy and a researcher from the Harvard School of Public Health, along with a team of investigators, set up a system for reducing heat casualties in military bases. Globe temperature diameter is a common variation as the specified diameter of 150mm is often inconvenient to use and transport. Smaller globes are greatly affected by air velocity in a way that is difficult to measure accurately and negates one of the original stated advantages of using the WBGT index that air velocity is not required. The WBGT index is still used today to regulate exposure to heat of US Marine Corps personnel.
