WBGT stands for Wet Bulb Globe Temperature and is a composite index used to assess thermal stress. It combines which of the following factors?

• A. Dry-bulb temperature, humidity, wind speed, and radiant heat.
• B. Dry-bulb temperature and humidity only.
• C. Wind speed and rainfall only.
• D. Radiant heat and wind speed only.

Answer: (A)

WBGT is built to reflect how hot it feels by bringing together air temperature, moisture in the air, radiant heat, and the cooling effect of wind. In practice, it uses measurements that capture these four aspects: dry-bulb temperature (air temperature), humidity (through the wet-bulb measurement which also accounts for evaporation and wind), and radiant heat (through globe temperature). The combination of these factors gives a single index of thermal stress. So the option that lists dry-bulb temperature, humidity, wind speed, and radiant heat is the best, because it includes all the components that drive heat strain. The other options omit one or more of these essential elements, such as radiant heat or wind/evaporative cooling.