The velocity and temperature fields of fire plumes are studied theoretically and computationally using the authors' large eddy simulation techniques. A version of the Navier-Stokes equations specialized to the study of fire dynamics is used as the basis for the analysis. No empirical turbulence modeling parameters are introduced into the computations. These simplifications permit high resolution solutions to the three dimensional time-dependent Navier-Stokes to be directly compared with experimental correlations of the time-averaged properties of an isolated vertical plume. Comparisons are made by averaging the time-dependent numerical results rather than the governing equations. Computed mean velocities and temperatures are shown to be in close agreement with McCaffrey's correlations. The methodology is then applied to the study of a large pool fire in an aircraft hangar with complicated roof geometry. A simple cell masking scheme permits the inclusion of the building geometry into the calculation without sacrificing computational efficiency. The plume structure in the hangar is compared with the isolated plume properties.