The Wet Bulb Globe Temperature (WBGT) is a measure of heat stress that takes into account various environmental factors such as temperature, humidity, wind speed, and radiant heat. It is commonly used to assess the risk of heat-related illnesses and to provide guidelines for activities in hot environments.
The WBGT index is derived from three temperature measurements:
Dry Bulb Temperature (DBT): This is the ambient air temperature measured with a standard thermometer.
Wet Bulb Temperature (WBT): This is the temperature measured by covering the bulb of a thermometer with a wet cloth and allowing it to evaporate. The rate of evaporation depends on the humidity, and the WBT provides an indication of the cooling effect of evaporation.
Globe Temperature (GT): This is the temperature measured using a black globe, which takes into account the radiant heat from the sun and surrounding surfaces.
The WBGT is calculated using a formula that incorporates these three temperatures, along with weighting factors for each component. The formula varies depending on the units used for temperature measurement (e.g., Celsius or Fahrenheit).
The WBGT is used to determine the risk level associated with heat exposure and helps in making decisions regarding work, physical activities, and sports in hot conditions. High WBGT values indicate increased heat stress and greater risk of heat-related illnesses such as heat exhaustion or heat stroke.
The effect of extreme heat, as indicated by high WBGT values, on survivability is significant. Prolonged exposure to extreme heat can lead to heat-related illnesses, which range from mild conditions such as heat cramps and heat exhaustion to severe and life-threatening conditions like heat stroke.
Heat stroke is a medical emergency characterized by a body temperature above 40°C (104°F) and is often accompanied by neurological symptoms. It can result in organ failure and, if not promptly treated, can be fatal. Heat-related illnesses can affect anyone, but certain individuals, such as the elderly, children, individuals with certain medical conditions, and those working in outdoor or physically demanding occupations, are particularly vulnerable.
Therefore, monitoring WBGT values and following guidelines for heat stress management, such as taking frequent breaks, staying hydrated, wearing appropriate clothing, and implementing cooling measures, is crucial for ensuring safety and reducing the risk of heat-related illnesses in extreme heat conditions.