Field models solve modeled conservation equations for mass, momentum, species and enthalpy in time-dependent turbulent flow driven by buoyancy. Detailed consideration is given to the sub models for the effects of buoyancy on turbulent transport and convective heat transfer, and for the combustion model on mean density and radiant emissivity. Improvements to existing state-of-the-art codes are suggested. Improving the credibility of field models requires a well-documented pedigree of validation of all sub models. Field models can give much needed qualitative and semi-quantitative information to both fire scientists and fire safety engineers. They can be expected to surpass zone models in use by the fire safety engineering profession in about five years.