WBGT (Wet Bulb Globe Thermometer), developed by Yaglou and Minard in 1957 (to control the exposure of US Navy personnel).
It establishes when a situation presents risks of thermal stress and helps take decisions about the preventive measures required to reduce them.
The name, WBGT, comes from the need to have the wet temperature, dry temperature and globe temperature values to calculate it. These are measured by means of a wet thermometer, a bulb thermometer and a globe thermometer, respectively.
It takes different variables into account such as humidity, wind, temperature and radiation (direct sun radiation like infrared emitted by bodies), indicating which activities are suitable and which are at unsupportable limits.