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By:  Ron Parker STS,CHST

As a safety professional and working on a job that is under a government contract you will be governed by the U.S. Army Corps of Engineers manual EM385-1-1.  One subject found in the EM385-1-1 that I will discuss is the Wet Bulb Globe Temperature (WBGT).  The WBGT is a composite temperature to estimate the temperature, humidity and solar radiation on humans.

In the late nineteen fifties, at the Marine base, Paris Island, S.C. several heat related incidents happened.  It was determined that high heat, high humidity and solar radiation led to these incidents.  The Department of Navy was commissioned to do a study on the effects of heat on humans while performing exercises. 

These studies resulted in a heat index called the Wet Bulb Globe Temperature (WBGT).  This was so effective in reducing heat related incidents it has become accepted in many workplaces, especially on Government contracted job sites, thus being integrated into the EM385-1-1.  In 1989 the WBGT was adopted as an international standard (ISO 7243).

WBGT instruments can be purchased commercially, however they can be rather expensive and require regular maintenance.  Less expensive equipment you can use that will do the job and produce the results you need are:

When engineering controls cannot control heat stress, another option is to limit the time personnel remain in the hot environment.  There are charts that can be obtained from local weather stations that list what clothing can be worn and time limits personnel can work, train or participate in sporting activities.  These charts will give WBGT readings and corresponding recommendations to prevent heat related incidents.  If buying costly equipment to arrive at the WBGT is not an option, here is a quick and effective formula for figuring the WBGT. 

What option you choose is up to you, however it is important to understand and implement the WBGT to ensure the safety of personnel.




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