This document serves as a general guide on how to approach and successfully calibrate a Picarro cavity ring-down spectrometer (CRDS). The steps described herein can be used on isotopic and/or concentration analyzers that measure CO₂, CO, CH₄, H₂O, C₂H₂, C₂H₄, C₂H₆, CH₂O, O₂ and N₂O. Additional analyzers may require special or extra steps to calibrate properly. If you are unsure if this document applies to your analyzer, please consult with Picarro support (support@picarro.com), your Picarro sales representative and Application Scientist.