WBGT

Wet Bulb Globe Temperature also known as WBGT is an index value computed in ˚C or ˚F, which provides information on the potential heat load of the environment.  It’s the measure of the heat stress in direct sunlight, which takes into account temperature, humidity, wind speed, sun angle and cloud cover. This is done by “measuring temperatures with a dry bulb thermometer, a wet bulb thermometer and a large, matte, black globe.”

“The temperature readings for the WBGT index combined according to one of two equations. For indoor work situations or for outdoor work where there is shade or cloud cover, and thus no solar heat load.”  Outdoor with solar radiation, WBGT is calculated for outdoor conditions as WBGT=0.7 Tnwb +0.2 Tg+ 0.1 Ta. This means the Wet Bulb Globe Temperature equals the natural wet bulb temperature plus the black globe temperature than ass the shade air temperature.  For “indoor temperature with negligible Solar Radiation the Wet Bulb Globe Temperature can be calculated as WBGT=0.7 Tnwb + 0.3 Tg.”

“Cold Stress is caused by the body’s inability to keep its inner temperature within the normal range.” Cold stress is more likely to occur during outdoor work during the seasons when wet or damp conditions are common and wind may contribute an additional cooling effect. According to the Occupational Safety and Health Administration “anyone working in a cold environment may be at risk for cold stress, some workers may be required to work outdoors in cold environments and for extended periods of time.” Cold stress can lead to serious health problems if not properly cared for. Heat stress occurs when people are over exposed to heat in work environments. “Exposure to extreme heat can result in occupational illnesses and injuries.” Heat stress can cause heat cramps, heat exhaustion, rash and if severe enough can cause a person to have a heat stroke.

https://www.osha.gov/SLTC/emergencypreparedness/guides/cold.html

Basics of Industrial Hygiene by Debra Nims