Fuel Moisture, Simplified: Introducing Vapor Pressure Deficit (VPD) on the Kestrel 5500FW Fire Weather Meter

Fuel Moisture, Simplified: Introducing Vapor Pressure Deficit (VPD) on the Kestrel 5500FW Fire Weather Meter

Fire weather management is an ever-evolving science, and professionals on the front lines know the importance of accurate, reliable data for effective decision-making. At Kestrel, we're proud to introduce a groundbreaking enhancement to the Kestrel 5500FW Fire Weather Meter - Vapor Pressure Deficit (VPD) measurement.

This new feature expands the meter's capabilities, equipping wildland firefighters and researchers with an advanced tool to better understand and manage fire weather conditions in the field.

What is Vapor Pressure Deficit (VPD)?

At its core, VPD measures the difference between the moisture content in the air and the maximum amount it can hold before saturation. In practical terms, it reveals the atmosphere's ability to "dry out" vegetation - an essential factor in wildfire behavior and fuel moisture (FM) levels.

For years, VPD has been a key metric in scientific research, helping to model and predict fire behavior. Now, we've made this advanced measurement accessible for real-time, field-based applications.

Why VPD Matters in Wildland Firefighting

Fuel moisture is the backbone of wildfire management. It influences every aspect of fire behavior, from ignition potential to spread rate and intensity. Traditional methods of measuring FM often require:

  • Collecting vegetation samples.
  • Transporting them for testing.
  • Drying them in a lab to determine moisture content.

With VPD integrated into the Kestrel 5500FW, these time-consuming processes can be reduced or even replaced. Firefighters and researchers can now estimate FM levels instantly, allowing them to focus on making critical decisions in the field.

Applications of VPD in the Field



  • Controlled Burns: VPD gives burn managers real-time data on atmospheric drying power, helping them adjust their strategies for safety and precision.
  • Wildfire Response: Quick FM estimates mean faster, more informed decision-making during dynamic situations.
  • Research & Education: By measuring VPD on-site, researchers can enhance FM modeling and publish data that supports advancements in wildfire science.

What Sets the Kestrel 5500FW Apart?

The Kestrel 5500FW has long been trusted for its rugged reliability and comprehensive weather measurements, including:

  • Temperature
  • Humidity
  • Wind speed and direction
  • Barometric pressure

Now, with the addition of VPD, this fire weather meter is poised to become an even more indispensable tool for wildfire professionals. The meter is also available as part of the Kestrel Fire Weather Kit, which includes all the accessories needed for accurate environmental monitoring in challenging field conditions.

Explore how the new VPD feature can elevate your fieldwork. Check out this video for a closer look at the Kestrel 5500FW and its VPD functionality, with key details highlighted at the 7:14 mark:

Watch the Video

Video courtesy of The World Of Wildland Fire (WETC)

At Kestrel, we're not just delivering products - we're empowering professionals with the tools they need to make informed decisions that save lives and protect communities. The addition of VPD to the 5500FW reflects our commitment to innovation and the ongoing advancement of fire weather management practices.