To predict the effect of fire on the structures, one needs to understand physics of the fire growth in a compartment as to how the fuel interacts with the flame and its surroundings. This study explores these effects and applies them to the common fuel configurations such as pool and crib fires. The focus on the study is on the fully-developed fires where all available fuel becomes involved to the maximum extent and can potentially yield the severest damage to the structural elements. A single-zone compartment fire model is developed along with a fuel mass loss rate model that accounts for the thermal enhancement, oxygen-limiting feedback, and the fuel type and configuration. A criterion for a one-zone, fully-developed fire is established and validated with experiments. An empirical correlation for mixing of oxygen into the lower floor layer essential for the modeling is also developed. An experimental program for single-wall-vent compartment using wood crib and heptane pool as fuels is carried out to validate the mathematical model and explore a full range of phenomena associated with fully developed fires: extinction, oscillation, fire area shrinkage, and response of fuel to thermal and oxygen effects. The simulation from the model is able to capture these phenomena and shows good agreement with the experiments. Some generalities of the fuel mass loss rate and compartment gas temperature are presented using the experimental results and the model simulations. The developed model has a potential to give burning time and temperature in a fire for any fuel, scale and ventilation.