...FDS is a computational fluid dynamics code that numerically solves a form of the Navier–Stokes equations for low-speed, thermally driven flow, with particular emphasis on smoke and heat transport from fires. It uses large-eddy simulation to represent complex fire-plume dynamics and can be applied to scenarios involving fire, wind, sprinklers, ventilation, geometry, materials, and other conditions that influence fire behavior. Users define a scenario through text-based input files, run the calculation with FDS, and analyze the resulting data. It displays output from FDS and CFAST simulations using OpenGL-based 3D graphics and scientific visualization methods, including animated smoke and tracer particles, two- and three-dimensional shaded contours, iso-surfaces, temperature fields, and flow vectors showing direction and magnitude.