Free Project Scorch – Fire Simulations in Buildings

From the Autodesk Labs website...

Project Scorch is a free* technology preview that helps users who need to perform fire simulations within a structure. Project Scorch uses the NIST Fire Dynamics Simulator to understand fire behavior within a building, such as smoke development and propagation, sprinkler behavior, and more. Project Scorch is a more efficient and easier to use front end for FDS from simulation set up and results exploration.

There's more information available on the Autodesk Labs website.