Kestrel 5400 Heat Stress WBGT Meter

The Kestrel 5400 Heat Stress Tracker is a user-friendly WBGT meter that detects when heat-related conditions are unsafe well before your body does.

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Product Documents


The most user-friendly WBGT meter on the market, the 5400 can detect when heat-related conditions are unsafe – well before your body does!


(Tripods sold separately)

  • K5400 Heat Stress + Vane Mount (Tan): 0854VTAN

  • K5400 Heat Stress Pro with Compass + LiNK + Vane Mount (TAN): 0854LVCTAN

  • K5400 Heat Stress (Orange): 0854ORA

  • K5400 Heat Stress + Vane Mount (Orange): 0854VORA

  • K5400 Heat Stress Pro with Compass + LiNK + Vane Mount (Orange): 0854LVCORA


Measures and Features

  • Wet Bulb Globe Temperature (“WBGT”)

  • Thermal Work Limit (“TWL”)

  • Waterless! Natural Wet Bulb Temperature accurately calculated from on-board digital sensors with no tedious setup or maintenance.

  • The large, hi-res, hi-contrast, graphic display is perfectly readable in the brightest sunlight and is backlit for use in low-light conditions.

  • Globe Temperature

  • Naturally Aspirated Wet Bulb Temperature

  • Wind Speed (Current, Average, & Maximum)

  • Altitude

  • Pressure trend

  • Barometric pressure

  • Relative humidity in %

  • Heat stress index

  • Dewpoint

  • Wet-bulb temperature

  • Density altitude

  • Wind chill

  • Air, water, and snow temperature °F or °C

  • Waterproof and floats

  • Time and date

  • Easy-to-read backlit display

  • Data Logger (automatic and manual)

  • Customizable data storage – 2900 data points

  • The humidity sensor can be calibrated in the field with our Relative Humidity Calibration Kit.

  • Customize screens to display user-selected measurements

  • Graph and recall trends

  • User-replaceable impeller

  • Data charting

  • Upload to a computer (with optional interface)

  • Meets MIL-STD-810F 516.5 Procedure IV Transit Shock test – 20 drops from 5 ft. IP-67 sealed to exclude dust and water at 3 ft. submersion

  • Five languages (English, French, Spanish, German, and Italian)

  • US Patent Nos. 5,783,753 and 5,939,645 and 6,257,074

  • Made in the USA

  • 5 Year Warranty


What’s new with the Kestrel 5400 over the Kestrel 4400/4600 it replaced

As for weather reading features, they will be the same.  You won’t get a ‘better’ temperature reading, wind reading, etc, or even more readings than available on the 4400/4600… still the same quality the USA made meter backed by a 5-year warranty.  That being said there are some pretty outstanding updates.

  • Flag warnings via loud buzzer & LED beacon!

  • Bluetooth LINK works with PC/Mac via Dongle

  • Bluetooth LINK to Smartphones / Mobiel / Android / IOS

  • Takes 1 AA battery (instead of 2 AAA)

  • The battery door is in the back, sealed away from the motherboard, should your battery leak as was common with all the 4000 series.  All 5000 battery doors are the same and interchangeable.

  • Slightly larger and improved higher contrast/resolution screen for any lighting (even sunlight) and easy on your eyes.

  • Intuitive user-interface screen navigation

  • Multiple Languages (English, French, German, Spanish)

  • Scratch and breakage-resistant window

  • All meters include both options of Red (NV – Night Vision) & White backlights.

  • Slightly bigger, more robust, though not really noticeable difference.

  • Roughly 10,000 data points.  4000 series all had under 5000 data points.

The Kestrel 5400 is revolutionary in size, cost and capability for those in need of measuring Heat Stress.  Available with or without LiNK (Bluetooth) and/or a compass.

Along with having a Wet Bulb Global Temperature reading, the Kestrel 5400 displays thermal work limit (“TWL”), another recognized composite heat stress prediction tool. For both WBGT and TWL, the Kestrel 5400 provides on-screen alarms when conditions enter the caution and danger zones, providing clear and immediate guidance that heat illness prevention steps must be taken.  Clothing levels can also be customized, making the Kestrel 4400 particularly useful in activities requiring heavy protective gear which worsens heat stress.  The Kestrel 5400 also displays natural wet bulb temperature and black globe temperature.

Athlete deaths from heat exposure are on the rise.   Warming summers have been accompanied by weekly reports of athletes young and old collapsing from severe heat-induced illness.  Our military training units struggle to keep soldiers healthy while preparing them for the gruelling heat of Iraq and Afghanistan.  OSHA is campaigning to prevent heat illness in outdoor workers and reports that every year thousands of workers become sick working in the heat, and some even die.  In every instance, the accurate and localized measurement of heat stress conditions is a key component of a heat illness prevention plan.  The Kestrel 5400 Heat Stress Tracker, new from NK, answers this need.

Human heat stress results from a combination of many environmental factors – air temperature and humidity along with radiant heat from the sun and surfaces, balanced by the cooling effect of breezes or airflow. Anyone who has stood under welcome shade adjacent to a sizzling parking lot understands that these conditions must be evaluated exactly where peoples’ activities are taking place.  The most common composite measurement used to determine appropriate exposure to heat stress conditions is Wet Bulb Globe Temperature or “WBGT.”  The American College of Sports Medicine, the American Conference of Governmental Industrial Hygienists, and the US Military all have published threshold limit values (TLV’s) or reference guidelines for conditions, activity levels and hydration based on WBGT, clothing levels and acclimatization of participants.


How Does the Kestrel 5400 Work?

The Kestrel 5400 uses a 1-inch black globe to gather information about the environment, which isn’t possible with current Kestrels. As is true with the original Wet Bulb Globe Temperature apparatus, a temperature sensor is installed inside the globe that will measure the temperature inside. The temperature inside the globe is a function of the ambient air temperature, solar insolation and wind speed.

As one can imagine, a sunny day will make the globe hotter because it’s painted black, and colder ambient temperatures will have a tendency to cool off the globe. Lastly, the wind will cause the globe to get closer to the ambient air temperature because it will carry heat away from the globe when the air is cooler, or increase heat transfer to the globe if the air is warmer than the globe.

The Kestrel must sit out for a period of time to allow the globe to adjust to true atmospheric conditions; we recommend a minimum of 7-10 minutes. The globe temperature is then taken into account along with other measurements, such as ambient temperature, humidity and pressure, to calculate more meaningful measurements, such as Wet Bulb Globe Temperature and Thermal Work Limit.

Indoor Use

Reading the WBGT is important even in indoor settings where heat stress is a concern.  The Kestrel has an ‘indoor’ setting on the WBGT setting which basically turns off the function of taking into account the direct solar radiation from the sun.  It’s important to place the Kestrel in a representative area of the conditions that the workers face.  Remember, wind plays a factor in WBGT, so a vane mount can be used indoors as well.  In the case of a ceiling fan, if the Kestrel doesn’t pick up the ceiling fan, then you are essentially getting the “worst-case” WBGT readings which is not actually a bad thing.  If the airflow is pretty strong from the fan and you want to have that factored in, you could mount the Kestrel sideways (vs vertical) so the impeller picks up the wind more realistically.  You can use the Clamp to achieve this.

Here is some good information on OSHA and WBGT values


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).

The heat index takes into consideration temperature and humidity and is calculated for shady areas.

There is a difference.

Monitoring the WBGT of the environment is quickly becoming the accepted and preferred method of measuring heat stress. Several sports organizations use WBGT to assess the potential risk of environmental stress on athletes. These organizations include the National Athletic Trainers Association (NATA), National Collegiate Athletic Association (NCAA) and the Women’s Tennis Association (WTA).

Thermal Work Limit (TWL) The unit will also display a measure of human heat stress known as “Thermal Work Limit” which, is measured in terms of the heat energy a person can dissipate from their surface area in Watts per square meter (w/m2). The measurement is based upon Globe Temperature, Relative Humidity, Ambient Temperature, Barometric Pressure, Wind Speed, and four parameters specific to an individual and their clothing. 4 Settings with preset constants are pre-installed in meter however for more specific applications:

Iclo: Intrinsic Clothing Insulation Factor 

Find out more

VPF: Vapor Permeation Factor

Find out more

  • For reference, values range between 0.37 – 0.45

  • 0.37 is a Long sleeve shirt/tweed suit jacket & long, loose trousers

  • 0.45 is shorts and a t-shirt

Pos: Position of the body

  • 1 for standing

  • 0 for lying down

Area: Area of a human male

  • Values are approximately 1.7m^2 or 1.8m^2

  • Meter assumes 1.7m^2


Compatible Apps

Kestrel LiNK for Windows & Mac

  • Kestrel LiNK for Windows

  • Kestrel LiNK for Mac(Coming Soon!)

Simple communication to Windows and Mac computers is provided through the optional LiNK.USB Dongle or USB Data Transfer Cable. Download your data to view, analyze and archive.  Enables the firmware update of Kestrel 5 series meters.

Kestrel LiNK for iOS & Android

  • Kestrel LiNK for iOS

  • Kestrel LiNK for Android

Wirelessly connect with iOS and Android devices.  When in range, view real-time measurements, receive on-screen alerts and download your data.  Logged data can be viewed, analyzed, archived and shared via e-mail, Facebook and Twitter.  Enables the firmware update of Kestrel 5 series meters. NOTE: Range up to 100’ line of sight – reduced by walls and obstructions.



  • Neck Lanyard

  • AA Lithium Battery (Average Life 400 Hours)

  • Protective Drawstring Pouch

  • Certificate of Conformity (with complete specifications)

  • Instruction Manual

  • Five Year Warranty

  • LiNK version also includes a sturdy zippered carry case

  • Kestrel 5400 Heat Stress (Orange): 0854ORA

  • Kestrel 5400 Heat Stress (Tan): 0854TAN

  • Kestrel 5400 Heat Stress + Vane Mount (Orange): 0854VORA

  • Kestrel 5400 Heat Stress + Vane Mount (Tan): 0854VTAN

  • Kestrel 5400 Heat Stress Pro with Compass and LiNK + Vane Mount (Orange): 0854LVCORA

  • Kestrel 5400 Heat Stress Pro with Compass and LiNK + Vane Mount (TAN): 0854LVCTAN

Additional information

Additional Info

(Tripods sold separately)K5400 Heat Stress + Vane Mount (Tan): 0854VTAN K5400 Heat Stress Pro with Compass + LiNK + Vane Mount

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