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Kestrel Meter 4400 Heat Stress Meter (DISCONTINUED)

by Kestrel

Kestrel Meter 4400 Heat Stress Meter (DISCONTINUED) - No Bluetooth Model

This product has been DISCONTINUED.  It has been replaced by the new Kestrel 5400.
The Kestrel 4400 Heat Stress Tracker was designed to help prevent human heat stress for those who work or train outdoors.  The Kestrel 4400 uses a 1 inch black globe to gather important environmental details that relate to human heat stress.  It measures Wet Bulb Globe Temperature (WBGT) and Thermal Work Limit (TWL)


The closest competitor in quality and accuracy in the heat stress market is the Quest, which costs about twice as much, nearly 10X the weight and size.  The Kestrel Heat Stress meters are revolutionizing an industry.


While the details of how the WBGT and TWL are calculated are proprietary to the US manufacturer at NK, here is what we can offer from the specification chart:


Outdoor Wet Bulb Globe Temperature (WBGT)

Measure of human heat stress defined as the combination of effects due to radiation, convection, and conduction. Outdoor WBGT is calculated from a weighted sum of natural wet bulb (Tnwb), globe temperature (Tg), and dry bulb temperature (Td). User settable on-screen warning zones.


Thermal Work Limit  (TWL)

Estimated safe maximum continuously sustainable human metabolic rate (W/m2) for the conditions and clothing factors. Based off of estimated metabolic output of typical human. On-screen zone warnings.

The portable meter allows users to create customized warning zones and alarms depending on their current work environment and also has the functionality to store different profiles.  It’s the perfect solution for those who have several different work sites, or who follow different standards depending on where they are training. Kestrel Wind Meters are used by NFL trainers to determine how frequently the athletes need to hydrate, and when the conditions are unhealthy for strenuous exercise.

4400 Features::

  • Thermal Work Limit (TWL)
  • Wet Bulb Globe Temperature (WBGT)
  • Naturally aspirated Wet Bulb Temperature
  • Wind speed
  • Max wind gust
  • Average wind speed
  • Temperature
  • Wind chill
  • Relative humidity
  • Heat stress index
  • Dew point temperature
  • Wet bulb temperature
  • Barometric pressure
  • Altitude
  • Density altitude
  • Pressure trend


The Kestrel 4000 is waterproof, able to float and includes an easy to read backlit display that shows the minimum, maximum and average values for every measure.  The automatic or manual data logging features makes it easy to store, recall, and graph data sets and customizable user screens allow users to group key measurements.  Data can be easily uploaded to a computer with an optional interface, allowing for easy storage and analysis of data for later use.


In addition to being easy to use, the Kestrel 4400 was also designed to be highly durable in the field.  The Kestrel 4400 features external temperature and humidity sensors for fast and accurate readings, and a patented “no-tools replaceable” wide-range air flow impeller that instantly restores the meter back to it’s factory calibration.  The meter was designed with a flip-top impeller cover that allows for the use of other functions while protecting the impeller.  The meter was built with a highly stable humidity sensor that rarely requires calibration.


Why Use WBGT as a Heat Stress Indicator vs. just using the Heat Index?

Wet bulb globe temperature (WBGT) is based on an equation that uses a combination of environmental elements to calculate the reading. The calculation is a measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle and cloud cover (solar radiation).

Heat index takes into consideration temperature and humidity, and is calculated for shady areas.


Customized Warning Zones

Users from different work environments or different standards around the world have the ability to create their own warnings on the Kestrel 4400.  With the user friendly functionality, the user may  go into the Kestrel 4400's WBGT function and turn different warning zones on or off and set these warning zones to be triggered at different degrees as the temperature rises. By customizing the Kestrel 4400's WBGT warning zones, monitoring a team or crew becomes much more personal. A chart with suggested warning zones will be included with every Kestrel 4400 ordered. 


The Kestrel 4400 includes:

  • Protective carry case
  • Kestrel Vane Mount
  • 2 AAA batteries
  • Kestrel Certificate of Conformity
  • 4400 HST (Heat Stress Tactical) are Berry Compliant with Vane Mount MOLLE Carry case.

It’s can be used in five different languages, including English, French, Spanish, German and Italian.


Kestrel 4400 Heat Stress Tracker Videos 

Kestrel Meter Heat Index Reference Guide

Download Heat Index Reference Guide - Download Now (PDF)


Kestrel Meter 4400 Additional Information 

*We ship every Kestrel 4000 Series Meter exclusively with Made in the USA Energizer® Brand Ultimate Lithium AAA batteries for improved reliability, capacity, cold-weather performance and weight. We strongly recommend that you use only Energizer Ultimate Lithium batteries in your Kestrel Meter. If you choose to install alkaline batteries, we recommend that you do NOT store your Kestrel with these batteries installed, and that you check your batteries for leakage and corrosion a minimum of every 30 days. Damage due to leaking alkaline batteries is not covered under warranty.