Health, Safety, Security and Environment

How is wind chill calculated?

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Q: How is wind chill calculated?

A: Heat stress is a commonly recognized problem, and many employers have put protective measures in place to reduce their workers’ risk of developing heart-related problems. Cold stress, however, is a much less widely discussed problem, yet cold stress can also have a devastating impact on the health and well-being of employees (learn more in Cold Stress: Your Winter Safety Guide). 

To guard against these risks, the Occupational Safety and Health Administration (OSHA) has put together recommendations for how long workers can work outside in cold conditions before needing breaks. This time period is determined by both the air temperature and the wind chill (which depends on how fast the wind is blowing).

Clearly, colder air temperatures and higher wind speeds mean that a worker is at a greater risk of cold stress. Cold stress can result in a wide range of damaging conditions, including frostbite and hypothermia. There are numerous guidelines for how to most effectively deal with frostbite —depending on the severity of the frostbite and the area of the body that is impacted by the frostbite. The most important thing is to stabilize the affected individual and get him/her to a medical provider as quickly and safely as possible. Hypothermia can also be life-threatening, leading to confusion, unconsciousness, and in some cases even death.

OSHA also notes that at some temperature and wind extremes, outdoor work should cease entirely (except for emergency work). For example, even with no wind, at temperatures of -45 degrees Fahrenheit or lower, outdoor work is not safe for employees — the risks are simply too high. Outdoor work should also stop at temperatures of -25 degrees Fahrenheit if the wind is stronger than 20 miles per hour.

Obviously workers with outdoor-only jobs are most at risk of developing cold stress. These workers could include oil and gas field workers, loggers, mining workers, and others. Many of these industries are clustered in areas that experience extremely harsh and cold weather conditions. However, these are not the only industries that may be impacted. Employers in other sectors of the economy must also be vigilant and take precautions to keep their workers safe when working outdoors

These precautions may range from providing high-quality protective weather gear to increasing the number of provided breaks per shift (as highlighted above). But, the most important steps that employers can take are: (1) being aware of up-to-the-minute weather information and (2) educating employees about warning signs of cold stress.

To be up-to-date on weather information, employers and employees need to be able to accurately calculate wind chill levels. To do this, they will need two pieces of information — the air temperature and wind speed. With these two pieces of information, the wind chill can be looked up in a comprehensive table that was created by the National Weather Service (http://www.nws.noaa.gov/om/cold/wind_chill.shtml). If this chart is not easily accessible, there is always a relatively straightforward formula that can be used to calculate the wind chill. This formula is:

Wind chill = 35.74 + 0.6215T -35.75(V^0.16) + 0.4275T(V^0.16)

Where T = temperature


V = wind speed in miles per hour

Knowing the wind chill at your job site will allow you to take the necessary precautions to keep your employees safe.

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