This report is a review of the mixing that occurs in fire induced gas flows through a doorway. The purpose of the report to provide a basis from which launch future experimental investigations. A detailed review is presented of the past research concerned with mixing in doorway flows. A number of fluid dynamic aspects associated with doorway flows are examined. The current zone model approximations, used to account for the mass transfer associated with vent flow mixing, are discussed. Theory for salt water modelling of fire induced gas flows through a compartment doorway is presented, and a relationship for the correct modelling of the volumetric flux is derived. This document concludes by detailing a number of specific aspects associated with doorway flows that require further research. An outline for future experimental work to be undertaken by the author is also presented.