A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy. / A theoretical and experimental treatment of fire processes in fuel-Lined, ventilated passages is presented. Initially a radially well mixed axial flow condition is considered. Experiments are first performed in non-stratified flow conditions where fire propagation and gas temperature histories are acquired from liquid and solid fuelled fires. Theory and experiment;display transient fire propagation for typical duct fire scenarios where initial fuel mass Loading is constant with respect to duct length. ( Abbreviation abstract ) / AC2017