Which three measurements are used in calculating WBGT?

• A. Dew point, relative humidity, and air velocity.
• B. Ambient temperature, surface temp, and wind chill.
• C. Solid temperature, liquid temperature, and gas temperature.
• D. Natural wet-bulb temperature, globe temperature, and dry-bulb (air) temperature.

Answer: (D)

WBGT combines how hot the air is, how humidity and evaporative cooling feel, and how much radiant heat is coming from the surroundings. The three measurements used are natural wet-bulb temperature, globe temperature, and dry-bulb (air) temperature. The dry-bulb temperature is simply the ambient air temperature. The natural wet-bulb temperature reflects evaporative cooling and humidity by letting a wetted wick evaporate; its value drops with lower humidity or more air movement, showing how humidity affects perceived heat. The globe temperature uses a black globe thermometer to measure radiant heat from the sun and surroundings, capturing radiant heat load. Using these three together allows WBGT to represent the combined effects of air temperature, humidity/evaporative cooling, and radiant heat on heat stress.