A low apparent temperature event and wind chill can be life threatening!
During the cold season and winter months, it’s important for leading contractors, owners and operators to understand the difference between a “low temperature event” and a “low apparent temperature event,” to enhance safety and manage risk on jobsites across the facility lifecycle, from new construction to ongoing operations and maintenance (O&M).
A low apparent temperature event is the “temperature equivalent” with the wind chill, as perceived by your project teams, trade craft and work crews outdoors in the field on your worksites. Further, an apparent temperature event accounts for numerous, other weather conditions and environmental factors such as relative humidity (RH) and wind speed, in addition to air temperature.
Without the proper precautions, a low apparent temperature event can lead to cold stress. Types of cold stress include immersion or trench foot, frostbite, and hypothermia. From time to time, the National Weather Service (NWS) issues wind chill advisories, potentially life threatening if preventive measures are not put in place. And, the NWS issues wind chill warnings, if life threatening.
The National Weather Service (NWS) describes how wind speeds accelerate heat loss from skin exposed to the elements. Wind chill or wind chill temperature (WCT) index measures the physiological effects of heat loss, with computer modeling to provide an “…accurate and understandable formula for calculating the dangers from winter winds and freezing temperatures.”
Further, the National Weather Service (NWS) Wind Chill Chart above shows the estimated frostbite times in 30-minute, 10-minute, and 5-minute increments, by air temperature and by wind speed. Based on a human face model, the wind chill chart incorporates heat transfer theory of heat loss from the body to its surroundings, during cold and breezy or windy days.
For more information about low apparent temperature events, wind chill, wind chill temperature (WCT) index, and cold stress, go to the OSHA webpage on winter weather.
More in the next blog series about weather planning, Weather Controls® and weather risk management for the construction industry and built environment…
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