The field model was adopted to three dimensional simulation of the time sequence of hot air temperature, wind vector, pressure and wall temperature in an early stage of a compartment fire, including generations and diffusions of smoke and toxic gases. This field model was applied to analysis of two model fire cases. One is a case of an early stage of a compartment fire from burn-up at a table extension up to the wall, and the other is a case of sudden hot air flow-out through a broken window by glass. Both cases were verified through the full scale experiments. The calculated values such as temperature and velocities agreed reasonably with the experimental results. In the latter case, the outward flow velocity showed remarkably strong outflow velocity after the window break as a character of "flash over”.