• three clear, sealable containers
• one container with magnesium chloride solution
• one container with sodium chloride solution
• two wooden scrapers
• an insulated carrying case to hold all of the above and maintain a stable environment while performing calibration
• For use with: Kestrel 4500, Kestrel 4300, Kestrel 4200, Kestrel 4100, Kestrel 4000, Kestrel 3500, and Kestrel 3000 (Both the older 2 button and 4 button version)

Factory Recalibration / Certification
The Kestrel should be recalibrated if the RH sensor has shown drift in its RH measurement.  The Kestrel RH sensor is specified to develop less than 2% drift over 24 months.  You may return your Kestrel meter to Nielson Kellerman (NK) for Factory Recalibration of the relative humidity and the related measurements.  Recalibration is available with and without certification of NIST traceability and calibration stickers.  NK can recalibrate and certify any of the values measured by your Kestrel meter, including: wind speed / air flow; temperature; barometric pressure and humidity.  Please contact NK for more information about Factory Recalibration and certification.

Field Recalibration
This Calibration Kit allows you to perform dozens of recalibrations in the field, to ensure that your Kestrel is always performing within specifications.  In fact, if using distilled water, you can calibrate an indefinite number of times. 
The manual explains in detail all of the steps for recalibrating your Kestrel. This process will take approximately 13 hours, including setup and calibration. 

How often should you calibrate your meter?

Largely it’s dependent on whether it’s industrial use or consumer use. Acousticians recalibrate annually, firefighters annually or semi-annually, and general consumers might recalibrate them every 4 or 5 years or so. The official stance is that a calibration is recommended every 24 months due to the possibility of up to 2% calibration drift over 24 months.

If you're Kestrel Meter is flashing 'E1', this means the humidity sensor needs to be re-calibrated. If the unit is less 30 days old (from the date of purchase) you may send it back to NK for re-calibration under warranty. If it has been more than 30 days from purchase, it can be returned to NK for a humidity calibration for $40 plus shipping.  OR - you can buy this calibration kit and do it yourself.