this study investigated one of the most important aspect of ultra-violet (uv) air disinfection modeling which is radiation modeling. radiation modeling is a topic of interest in the domain of uv air disinfection research. researchers in this field uses various types of radiation models to perform radiation modeling work including: multiple point source summation (mpss), multiple segment source summation (msss), line source integration (lsi), view factor model and discrete ordinate (do) model; among the radiation models discussed, do model is the only numerical iterative radiation model that can fully utilize the ever increasing power of computing,of today. advantages of properly utilizing the do model for radiation modeling include solving complex radiation problems in a full 3-dimensional space that provides ways to study fluence rate distribution easily. this work aims to properly utilize and validate the do model by: • demonstrating do model’s consideration for basic optical principles (refraction, reflection, shadowing effecting and partial absorption) • studying fluence rate simulated values by comparing it with previously published experimental work • performing a 3-dimensional multi-lamp radiation experiment in conjunction with the complex do model radiation simulation case setup the work performed shows that do model is capable of considering basic optical principles (refraction, reflection, shadowing effecting and partial absorption) which are all integral to developing an accurate radiation model. previously published use of the do model in fluence rate studies concluded that do model was inaccurate because some of the basic optical considerations could not be included in the solution; however, the findings of this work prove otherwise. a detailed description of utilizing do model to account for these optical principles was outlined in this paper. with sufficient understanding of utilizing the do model for uv lamp radiation cases, the scalability of using this newly described method to solve complex uv radiation cases was demonstrated. additionally, do model simulated results (with all basic optical considerations) are shown to match uv fluence rate values based on a published actinometer radiation experiment to a good agreement. this method was studied further by performing a complex multi lamp 3d radiation experiment and comparing the experimental readings to the do model simulated result. the complexity of this uv radiation experiment is unprecedented as there are no published uv radiation lamp experimental work that could be found (during the time of writing). unfortunately, the comparison between radiometer readings and simulated values did not show good agreement. although the do model simulation results did not match the experimentally measured data completely, a lot of important optical considerations to include in a do model simulation was explored. findings from this study is significant to the application and utilization ofdo model in radiation modeling work for uv air disinfection.