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Wet Bulb Globe Temperature Thresholds 2012 / White paper
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Summary
Executive summary .................................................................................... p 1
Introduction ................................................................................................ p 2
Who uses the wet bulb globe temperature indicator? .................................. p 4
State-of-the-art of wet bulb globe temperature ............................................ p 6
User benefits with Schneider Electric’s industry-unique solution ................... p 8
Conclusion ................................................................................................. p 9
Executive summary
Heat stress is a common challenge to athletes and a significant safety issue for
their trainers, coaches and managers. Professional sport organizations, including
the National Collegiate Athletic Association (NCAA) and the National Athletic
Trainers Association (NATA), recommend they follow safety protocols based on
wet bulb globe temperature thresholds. Some state high school associations are
identifying fines for violations of wet bulb globe temperature thresholds to
enforce compliance.
While there are dedicated sensors for determining wet bulb globe temperature,
they are expensive and single-purpose and do not provide any information beyond
the wet bulb globe temperature at the time of reading. Schneider Electric’s
popular MxVision WeatherSentry Online® service now includes the wet bulb globe
temperature reading for the user’s location, using a scientifically-based calculation.
It also provides wet bulb globe temperature forecasts, based on its own industry-
best temperature forecasts, along with proactive alerts based on the user’s
specified thresholds. It is the first and only marketed service that provides wet bulb
globe temperature forecasts and alerts that help the organization prepare and/
or revise training and practice schedules and activities as needed to comply with
relevant safety protocols.
This unique functionality eliminates the need for the organization to purchase,
deploy and maintain expensive equipment specific for wet bulb globe temperature
determination. Its inclusion in the notably reliable Schneider Electric weather
information service further supports decision making by those responsible for
athlete safety.
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Wet Bulb Globe Temperature Thresholds
Introduction
Wet bulb globe temperature is a composite temperature indicator, calculated
using a formula that factors the effect of temperature, humidity, wind speed, and
solar radiation on humans. It is a more comprehensive measure than the heat
index, or ‘feels-like factor’, which reflects air temperature and relative humidity
measured in the shade. The heat index commonly is referred to as the human-
perceived equivalent temperature — ‘how hot it feels’ — to a person who is
normally dressed and not involved in strenuous activity.
Yet, because the wet bulb globe temperature calculation reflects measurements
taken in the sun and embraces wind, cloud cover and sun angle, wet bulb globe
temperature is considered the better measure of heat stress on the human body.
In this paper, we discuss how the wet bulb globe temperature indicator is used
by sports organizations and why Schneider Electric’s weather information service
provides the wet bulb globe temperature measurement that best meets their
safety protection needs.
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Wet Bulb Globe Temperature Thresholds
An unmatched service offering to protect all athletes
Who uses the wet bulb globe temperature indicator?The Women’s Tennis Association (WTA), National
Athletic Trainers Association (NATA) and National
Collegiate Athletic Association (NCAA) all identify
both wet bulb globe temperature and heat index in
their respective rules and procedures as acceptable
metrics for decision-making purposes; see Table 1.
However, wet bulb globe temperature is fast
becoming the most widely used and accepted index
for the assessment of heat stress in sports and
turf activities, from student-level up to professional
organizations; see Table 2. It also is used in military
operations, and the federal Occupational Safety and
Health Administration (OSHA) maintains heat safety
protocols based on wet bulb globe temperature
thresholds that provide guidance to outdoors-
focused sectors, such as construction operations.
Essentially, anyone who works or exercises in direct
sunlight should monitor wet bulb globe temperature.
Studies reveal there is an increase in the number
of heat-related injuries when the wet bulb globe
temperature reaches/exceeds 82 degrees Fahrenheit.
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Wet Bulb Globe Temperature Thresholds
Organization Wet Bulb Globe
Temperature
decision points, in
degrees Fahrenheit
Heat Index
decision points,
in degrees
Fahrenheit
WTA 86.2, 90 93, 104.2
NATA 65, 73, 82 87, 90, 115
NCAA 75, 82 77, 87
National Weather
Service
Not used 90, 104, 126
Table 1Wet bulb globe temperature — a new standard for measuring environmental heat stress
Wet Bulb Globe Temperature
Heat Index
Measured in the sun
a x
Measured in the shade
x a
Uses temperature
a a
Uses relative humidity
a a
Uses wind a x
Use cloud cover
a x
Uses sun angle
a x
Who uses the wet bulb globe temperature indicator, continued…
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Wet Bulb Globe Temperature Thresholds
* Adopted on March 19, 2012, by the State Executive Committee and goes into effect for the 2012-13 school year.
Table 2Georgia High School Association (GHSA) Practice Policy for Heat and Humidity*
Wet Bulb Globe
Temperature Reading
Activity Guidelines & Rest Break Guidelines
Under 82.0 Normal activities — provide at least three separate
rest breaks each hour of minimum duration of three
minutes each during workout
82.0 — 87.0 Use discretion for intense or prolonged exercise;
watch at-risk players carefully; provide at least three
separate rest breaks each hour of a minimum of
four minutes duration each
87.0 — 89.9 Maximum practice time is two hours. For football:
players restricted to helmet, shoulder pads, and
shorts during practice. All protective equipment
must be removed for conditioning activities. For all
sports: provide at least four separate rest breaks
each hour of a minimum of four minutes each
90.0 — 92.0 Maximum length of practice is one hour, no
protective equipment may be worn during practice
and there may be no conditioning activities. There
must be 20 minutes of rest breaks provided during
the hour of practice.
Over 92.1 No outdoor workouts; cancel exercise; delay
practices until a cooler wet bulb globe temperature
reading occurs.
In 2012, the Georgia High School Association
(GHSA) passed new laws* defining statewide policy
for conducting practices and voluntary conditioning
workouts in all sports during times of extremely high
heat and/or humidity:
• Rest time should involve both unlimited hydration
intake (water or electrolyte drinks) and rest
without any activity involved
• For football, helmets should be removed during
rest time
• The site of the rest time should be a ‘cooling
zone’ and not in direct sunlight
• When the wet bulb globe temperature reading is
over 86:
• Ice towels and spray bottles filled with ice
water should be available at the ‘cooling zone’
to aid the cooling process
• Cold immersion tubs must be available for
practices for the benefit of any player showing
early signs of heat illness
Schools violating the heat policy can be fined from
$500 to $1000 per occurrence.
State-of-the-art of wet bulb globe temperatureTraditionally, organizations measure wet bulb globe temperature with expensive,
on-site sensors that provide the temperature indicator at the moment, for
the specific location of the sensor, with no visability to future wet bulb globe
temperature readings. The accuracy of these sensors can vary.
Now, Schneider Electric’s popular MxVision WeatherSentry Online weather
information service incorporates not only wet bulb globe temperature
observations, but also reliable wet bulb globe temperature forecasts and alert
notifications that help organizations adhere to safety guidelines:
• Observations — the user can view the observed wet bulb globe temperature
for a specific area, calculated using peer-reviewed, published methodology
that does not rely on specialized sensors.1 These observations are displayed
within the site’s layered map, as shown in Figure 1.
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Wet Bulb Globe Temperature Thresholds
Figure 1MxVision WeatherSentry Online provides a wet bulb globe temperature map layer for observed wet bulb globe temperature.
1 Estimation of Black Globe Temperature for Calculation of the Wet Bulb Globe Temperature Index. Proceedings of the World Congress on Engineering and Computer Science 2011, Vol II WCECS 2011, October 19-21, 2011, San Francisco, USA.
State-of-the-art of wet bulb globe temperature, continued…
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Wet Bulb Globe Temperature Thresholds
• Forecasts — forecasts for wet bulb globe
temperature are available in hourly and daily
forecasts; see Figure 2. Schneider Electric is the
first and only service to make available hourly
wet bulb globe temperature forecasts out to
72 hours. It also provides daily wet bulb globe
temperature forecasts out to 15 days, for long-
term planning purposes.
• Alerts — proactive alerts based on the user’s
wet bulb globe temperature thresholds are
delivered to the user’s computer or mobile device
via patented, location-specific technology;
see Figure 3. Many users set up observation
or forecast alerts based on NCAA, NATA, or
other established heat safety protocols. These
alerts provide the lead time necessary to
adjust schedules as needed to assure athlete
safety. Again, alerts based on wet bulb globe
temperature forecasts are exclusive to Schneider
Electric’s MxVision WeatherSentry Online service.
Figure 2Exclusive from Schneider Electric, hourly and daily wet bulb globe temperature forecasts allow sports managers to plan when activities might be limited due to the heat.
Figure 3A proactive alert notifies the user, via computer or mobile device, when the wet bulb globe temperature exceeds or is expected to exceed the organization’s identified threshold.
User benefits with Schneider Electric’s industry-unique solution
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Wet Bulb Globe Temperature Thresholds
Accuracy. A recent, independent study conducted
by ForecastWatch.com identified Schneider Electric
as the most accurate temperature forecaster among
leading providers for Day 1 and Day 2 temperature
forecasts. This study signals the fifth consecutive
year Schneider Electric has been ranked best in
temperature forecast accuracy. These temperature
forecasts are a key element in the service’s industry-
unique wet bulb globe temperature forecasts.
Reliability. The MxVision WeatherSentry Online service
eliminates the need for the organization to purchase
and maintain expensive, single-function equipment.
Efficiency. With hourly wet bulb globe temperature
forecasts provided for 72 hours out, the sports
organization is able to plan effectively and realize the
most efficiency in conducting its training and practice
activities and competitive events.
Around-the-clock online meteorological consulting.
Users can submit a weather-related question
to Schneider Electric’s team of professional
meteorologists and receive a response back within
15 minutes. For example, the user might ask “What
is your confidence in the wet bulb globe temperature
forecast between 2 to 4 p.m. today, which calls for
the wet bulb globe temperature to be higher than 82
degrees?” See Figure 4.
Figure 4Online consulting allows users to contact professional meteorologists to gain expert insight to specific weather questions and concerns.
Conclusion
Wet bulb globe temperature solutions, in summary:
• Wet bulb globe temperature is being adopted by more sports organizations as
their standard for identifying possible heat-related risks to athletes.
• It better represents the potential of environmental heat stress than does the
traditional heat index indicator, because it factors the wind, cloud and
sun-angle factors significant when athletes are exerting themselves at a facility
with no sun cover.
• Thousands of sports and recreation organizations — including high school,
university, and professional sports teams — already rely on Schneider Electric’s
real-time weather conditions and reliable forecasts to ensure player, spectator,
and employee safety.
• This service now includes current and forecasted wet bulb globe temperature
readings, along with proactive alerting to notify users when their specified
thresholds exist or are forecast.
• This industry-unique functionality, along with all other current and forecast
weather information provided to help protect athletes, spectators and staff,
makes the Schneider Electric weather service a comprehensive solution
that provides value far beyond that delivered by dedicated wet bulb globe
temperature equipment.
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Wet Bulb Globe Temperature Thresholds
Schneider Electric USA, Inc.
9110 West Dodge RoadOmaha NE 68114 Tel: 800-610-0777Fax: 402-255-8125www.schneider-electric.com/us ©
2012
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July 2012