CFAST 6.2.1 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The latest version of CFAST is supported on PCs running Windows XP/Vista/7/8/10/11, 32-bit.
Commonly, this program's installer has the following filename: CEdit.exe. According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. The most popular versions among CFAST users are 6.2, 6.1 and 6.0. The software lies within Education Tools, more precisely Science Tools. This free program is a product of NIST.
From the developer:
The Consolidated Model of Fire and Smoke Transport, CFAST, is a computer program that fire investigators, safety officials, engineers, architects and builders can use to simulate the impact of past or potential fires and smoke in a specific building environment. CFAST is a two-zone fire model used to calculate the evolving distribution of smoke, fire gases and temperature throughout compartments of a building during a fire.
You may want to check out more software, such as Full Format and Refresh Tool or NIST FDS and Smokeview, which might be related to CFAST.