This supplement to the CFAST Technical Reference Guide provides details of the software development process for CFAST and accompanying validation for the model. It is based in part on the Standard Guide for Evaluating the Predictive Capability of Deterministic Fire Models, ASTM E 1355. The model evaluation process consists of two main components: verification and validation. Verification is a process to check the correctness of the solution of the governing equations. Verification does not imply that the governing equations are appropriate; only that the equations are being solved correctly. Validation is a process to determine the appropriateness of the governing equations as a mathematical model of the physical phenomena of interest. Typically, validation involves comparing model results with experimental measurement. Differences that cannot be explained in terms of numerical errors in the model or uncertainty in the measurements are attributed to the assumptions and simplifications of the physical model. Evaluation is critical to establishing both the acceptable uses and limitations of a model. Throughout its development, CFAST has undergone various forms of evaluation, both at NIST and beyond. This Supplement provides a survey of validation work conducted to date to evaluate CFAST. Documentation of CFAST Verification is contained in the CFAST Technical Reference Guide