As an athletic trainer or director, ensuring the safety of your athletes during practices and games is a top priority. One major aspect is monitoring the Wet Bulb Globe Temperature (WBGT), which helps determine the risk of heat-related illnesses. While Kestrel devices are widely used for WBGT monitoring, recent studies have raised concerns about their accuracy and the potential impact on athletic activities.

For example, at a WBGT of 86°F, about 75% of Kestrel 5400 readings are higher than the actual WBGT, and this disparity reaches nearly 100% at a WBGT of 92°F.

Multiple independent studies have found that nearly 40% of the Kestrel readings would have resulted in restricting athletic activity when the ISO standard device showed activities could safely continue.

Reasons Behind the Inaccuracy 

Several factors contribute to the Kestrel 5400’s inaccurate readings. 

One issue is that the device heats up in the sun, resulting in elevated temperature readings. Kestrel’s own information calls out this issue. 

Lack of Solar Radiation Shield

Kestrels’ temperature and humidity sensors are not properly shielded from solar radiation. This causes the temperature sensor to read higher than the true ambient air temperature when exposed to direct sunlight, resulting in erroneously high WBGT readings.

Why the Size of the Black Bulb Matters

The size of the black bulb matters when measuring Wet Bulb Globe Temperature (WBGT) because it affects the globe temperature reading, which is a key component of the WBGT calculation. Here’s why: 

1. Heat Absorption: A larger bulb absorbs more radiant heat, leading to higher globe temperature readings. 
2. Response Time: A larger bulb’s higher heat absorption threshold enables more stable response times, making it a much more reliable measure of globe temperature readings and minimizing frequent, and often inaccurate, spikes in readings.
3. Convective Cooling: A larger bulb experiences less convective cooling, which can further increase globe temperature readings.

Learn more about black bulb sensors and how they work here.

Impact on Athletic Activities 

The inaccuracies in WBGT readings can have a significant impact on athletic practices and games. 

While it’s better to err on the side of caution, excessive overestimation of WBGT can lead to unnecessary practice cancellations, disrupting training schedules and acclimatization plans.

Impracticality For Use in The Field

Handheld WBGT devices can be inconvenient for athletic trainers who are required to take and document readings every hour, as mandated by many states like Georgia and California. Some drawbacks include:

1. Setup time: Handheld devices often need 10-20 minutes for sensors to equilibrate with the environment before providing accurate readings. 
2. Frequent adjustments: Accurate measurements require holding the device at the correct height and orientation, which can be tiresome and requires frequent adjustments. 
3. Limited data logging: Many handheld devices have limited or no data logging capabilities, forcing users to manually record measurements, which is time-consuming and error-prone. 

These factors make handheld WBGT devices less practical for consistent, long-term monitoring and documentation of environmental conditions.

Lack of Warning Functionality

When WBGT monitors like Kestrel are used for student athletics, they often require immediate responses or alterations to practices or games when WBGT temperatures reach certain heat stress policy thresholds. This results in Athletic Trainers or those responsible for ensuring compliance with heat stress policies needing to communicate with many people simultaneously. 

Kestrel cannot alert coaches and athletes of what practice alterations are required. Products like Perry Weather integrate school heat stress policies into the platform and automatically send text messages and mobile push notifications to everyone on campus with concise instructions on what alterations are required. 

In conclusion, accurate WBGT monitoring is crucial for ensuring the safety of athletes during practices and games. As an athletic trainer or director, it is essential to be aware of the potential inaccuracies in Kestrel devices and to consider alternative options that provide more reliable and precise WBGT readings. By investing in the right professional-grade equipment and utilizing it properly, you can optimize safety while maximizing practice productivity.

Learn more about how Perry Weather monitors WBGT and alerts you when heat stress policies are reached.

Ensuring Accurate WBGT Monitoring 

To ensure the safety of your athletes, it is essential to use reliable and accurate WBGT monitoring devices. On-site devices that utilize meteorological-grade sensors are the best option for obtaining actionable data. When choosing a WBGT monitoring system, look for reputable commercial-grade devices that adhere to ISO safety standards and provide maximum accuracy under sunny and humid conditions. Proper installation, calibration, and maintenance of these devices are also crucial to maintain precision throughout the season.

Learn more about Perry Weather 

Perry Weather offers accurate and done-for-you WBGT measuring and monitoring, providing solutions and features like an outdoor weather station, customizable alerts, policy consultations, and 24/7 on-call meteorologist support.  We ensure you can provide comprehensive heat safety to those you’re responsible for. If you’d like to better understand how Perry Weather can elevate your WBGT monitoring and ensure safety, contact us to learn more.